MEM: Separate requests and responses for timing accesses

This patch moves send/recvTiming and send/recvTimingSnoop from the
Port base class to the MasterPort and SlavePort, and also splits them
into separate member functions for requests and responses:
send/recvTimingReq, send/recvTimingResp, and send/recvTimingSnoopReq,
send/recvTimingSnoopResp. A master port sends requests and receives
responses, and also receives snoop requests and sends snoop
responses. A slave port has the reciprocal behaviour as it receives
requests and sends responses, and sends snoop requests and receives
snoop responses.

For all MemObjects that have only master ports or slave ports (but not
both), e.g. a CPU, or a PIO device, this patch merely adds more
clarity to what kind of access is taking place. For example, a CPU
port used to call sendTiming, and will now call
sendTimingReq. Similarly, a response previously came back through
recvTiming, which is now recvTimingResp. For the modules that have
both master and slave ports, e.g. the bus, the behaviour was
previously relying on branches based on pkt->isRequest(), and this is
now replaced with a direct call to the apprioriate member function
depending on the type of access. Please note that send/recvRetry is
still shared by all the timing accessors and remains in the Port base
class for now (to maintain the current bus functionality and avoid
changing the statistics of all regressions).

The packet queue is split into a MasterPort and SlavePort version to
facilitate the use of the new timing accessors. All uses of the
PacketQueue are updated accordingly.

With this patch, the type of packet (request or response) is now well
defined for each type of access, and asserts on pkt->isRequest() and
pkt->isResponse() are now moved to the appropriate send member
functions. It is also worth noting that sendTimingSnoopReq no longer
returns a boolean, as the semantics do not alow snoop requests to be
rejected or stalled. All these assumptions are now excplicitly part of
the port interface itself.

47 files changed, 535 insertions, 413 deletions

diff --git a/src/arch/x86/pagetable_walker.cc b/src/arch/x86/pagetable_walker.cc
index 960954f15..b6e6c33f4 100644
--- a/src/arch/x86/pagetable_walker.cc
+++ b/src/arch/x86/pagetable_walker.cc
@@ -114,15 +114,14 @@ Walker::startFunctional(ThreadContext * _tc, Addr &addr, unsigned &logBytes,
 }
 
 bool
-Walker::WalkerPort::recvTiming(PacketPtr pkt)
+Walker::WalkerPort::recvTimingResp(PacketPtr pkt)
 {
-    return walker->recvTiming(pkt);
+    return walker->recvTimingResp(pkt);
 }
 
 bool
-Walker::recvTiming(PacketPtr pkt)
+Walker::recvTimingResp(PacketPtr pkt)
 {
-    assert(pkt->isResponse());
     WalkerSenderState * senderState =
         dynamic_cast<WalkerSenderState *>(pkt->senderState);
     pkt->senderState = senderState->saved;
@@ -171,7 +170,7 @@ Walker::recvRetry()
 bool Walker::sendTiming(WalkerState* sendingState, PacketPtr pkt)
 {
     pkt->senderState = new WalkerSenderState(sendingState, pkt->senderState);
-    return port.sendTiming(pkt);
+    return port.sendTimingReq(pkt);
 }
 
 MasterPort &
diff --git a/src/arch/x86/pagetable_walker.hh b/src/arch/x86/pagetable_walker.hh
index c4c770884..9392290c7 100644
--- a/src/arch/x86/pagetable_walker.hh
+++ b/src/arch/x86/pagetable_walker.hh
@@ -70,12 +70,12 @@ namespace X86ISA
           protected:
             Walker *walker;
 
-            bool recvTiming(PacketPtr pkt);
+            bool recvTimingResp(PacketPtr pkt);
 
             /**
              * Snooping a coherence request, do nothing.
              */
-            bool recvTimingSnoop(PacketPtr pkt) { return true; }
+            void recvTimingSnoopReq(PacketPtr pkt) { }
             Tick recvAtomicSnoop(PacketPtr pkt) { return 0; }
             void recvFunctionalSnoop(PacketPtr pkt) { }
             void recvRetry();
@@ -179,7 +179,7 @@ namespace X86ISA
         MasterID masterId;
 
         // Functions for dealing with packets.
-        bool recvTiming(PacketPtr pkt);
+        bool recvTimingResp(PacketPtr pkt);
         void recvRetry();
         bool sendTiming(WalkerState * sendingState, PacketPtr pkt);
 
diff --git a/src/cpu/base.cc b/src/cpu/base.cc
index edbec8c80..c942cad44 100644
--- a/src/cpu/base.cc
+++ b/src/cpu/base.cc
@@ -532,7 +532,7 @@ BaseCPU::traceFunctionsInternal(Addr pc)
 }
 
 bool
-BaseCPU::CpuPort::recvTiming(PacketPtr pkt)
+BaseCPU::CpuPort::recvTimingResp(PacketPtr pkt)
 {
     panic("BaseCPU doesn't expect recvTiming!\n");
     return true;
diff --git a/src/cpu/base.hh b/src/cpu/base.hh
index f94c5e0a4..5d88e064b 100644
--- a/src/cpu/base.hh
+++ b/src/cpu/base.hh
@@ -133,7 +133,7 @@ class BaseCPU : public MemObject
 
       protected:
 
-        virtual bool recvTiming(PacketPtr pkt);
+        virtual bool recvTimingResp(PacketPtr pkt);
 
         virtual void recvRetry();
 
diff --git a/src/cpu/inorder/cpu.cc b/src/cpu/inorder/cpu.cc
index 04176c54f..7e75dfbb8 100644
--- a/src/cpu/inorder/cpu.cc
+++ b/src/cpu/inorder/cpu.cc
@@ -88,10 +88,8 @@ InOrderCPU::CachePort::CachePort(CacheUnit *_cacheUnit) :
 { }
 
 bool
-InOrderCPU::CachePort::recvTiming(Packet *pkt)
+InOrderCPU::CachePort::recvTimingResp(Packet *pkt)
 {
-    assert(pkt->isResponse());
-
     if (pkt->isError())
         DPRINTF(InOrderCachePort, "Got error packet back for address: %x\n",
                 pkt->getAddr());
diff --git a/src/cpu/inorder/cpu.hh b/src/cpu/inorder/cpu.hh
index 06d733d85..bb52c6023 100644
--- a/src/cpu/inorder/cpu.hh
+++ b/src/cpu/inorder/cpu.hh
@@ -170,13 +170,13 @@ class InOrderCPU : public BaseCPU
       protected:
 
         /** Timing version of receive */
-        bool recvTiming(PacketPtr pkt);
+        bool recvTimingResp(PacketPtr pkt);
 
         /** Handles doing a retry of a failed timing request. */
         void recvRetry();
 
         /** Ignoring snoops for now. */
-        bool recvTimingSnoop(PacketPtr pkt) { return true; }
+        void recvTimingSnoopReq(PacketPtr pkt) { }
     };
 
     /** Define TickEvent for the CPU */
diff --git a/src/cpu/inorder/resources/cache_unit.cc b/src/cpu/inorder/resources/cache_unit.cc
index a5bb9cd24..a4dc23d47 100644
--- a/src/cpu/inorder/resources/cache_unit.cc
+++ b/src/cpu/inorder/resources/cache_unit.cc
@@ -873,7 +873,7 @@ CacheUnit::doCacheAccess(DynInstPtr inst, uint64_t *write_res,
             tid, inst->seqNum, cache_req->dataPkt->getAddr());
 
     if (do_access) {
-        if (!cachePort->sendTiming(cache_req->dataPkt)) {
+        if (!cachePort->sendTimingReq(cache_req->dataPkt)) {
             DPRINTF(InOrderCachePort,
                     "[tid:%i] [sn:%i] cannot access cache, because port "
                     "is blocked. now waiting to retry request\n", tid, 
diff --git a/src/cpu/o3/cpu.cc b/src/cpu/o3/cpu.cc
index fe70c3fcf..e8fc968b7 100644
--- a/src/cpu/o3/cpu.cc
+++ b/src/cpu/o3/cpu.cc
@@ -87,9 +87,8 @@ BaseO3CPU::regStats()
 
 template<class Impl>
 bool
-FullO3CPU<Impl>::IcachePort::recvTiming(PacketPtr pkt)
+FullO3CPU<Impl>::IcachePort::recvTimingResp(PacketPtr pkt)
 {
-    assert(pkt->isResponse());
     DPRINTF(O3CPU, "Fetch unit received timing\n");
     // We shouldn't ever get a block in ownership state
     assert(!(pkt->memInhibitAsserted() && !pkt->sharedAsserted()));
@@ -107,18 +106,16 @@ FullO3CPU<Impl>::IcachePort::recvRetry()
 
 template <class Impl>
 bool
-FullO3CPU<Impl>::DcachePort::recvTiming(PacketPtr pkt)
+FullO3CPU<Impl>::DcachePort::recvTimingResp(PacketPtr pkt)
 {
-    assert(pkt->isResponse());
-    return lsq->recvTiming(pkt);
+    return lsq->recvTimingResp(pkt);
 }
 
 template <class Impl>
-bool
-FullO3CPU<Impl>::DcachePort::recvTimingSnoop(PacketPtr pkt)
+void
+FullO3CPU<Impl>::DcachePort::recvTimingSnoopReq(PacketPtr pkt)
 {
-    assert(pkt->isRequest());
-    return lsq->recvTimingSnoop(pkt);
+    lsq->recvTimingSnoopReq(pkt);
 }
 
 template <class Impl>
diff --git a/src/cpu/o3/cpu.hh b/src/cpu/o3/cpu.hh
index be51f415f..41128110b 100644
--- a/src/cpu/o3/cpu.hh
+++ b/src/cpu/o3/cpu.hh
@@ -148,8 +148,8 @@ class FullO3CPU : public BaseO3CPU
 
         /** Timing version of receive.  Handles setting fetch to the
          * proper status to start fetching. */
-        virtual bool recvTiming(PacketPtr pkt);
-        virtual bool recvTimingSnoop(PacketPtr pkt) { return true; }
+        virtual bool recvTimingResp(PacketPtr pkt);
+        virtual void recvTimingSnoopReq(PacketPtr pkt) { }
 
         /** Handles doing a retry of a failed fetch. */
         virtual void recvRetry();
@@ -176,8 +176,8 @@ class FullO3CPU : public BaseO3CPU
         /** Timing version of receive.  Handles writing back and
          * completing the load or store that has returned from
          * memory. */
-        virtual bool recvTiming(PacketPtr pkt);
-        virtual bool recvTimingSnoop(PacketPtr pkt);
+        virtual bool recvTimingResp(PacketPtr pkt);
+        virtual void recvTimingSnoopReq(PacketPtr pkt);
 
         /** Handles doing a retry of the previous send. */
         virtual void recvRetry();
diff --git a/src/cpu/o3/fetch_impl.hh b/src/cpu/o3/fetch_impl.hh
index 2480211e4..f4ce77f22 100644
--- a/src/cpu/o3/fetch_impl.hh
+++ b/src/cpu/o3/fetch_impl.hh
@@ -621,7 +621,7 @@ DefaultFetch<Impl>::finishTranslation(Fault fault, RequestPtr mem_req)
         fetchedCacheLines++;
 
         // Access the cache.
-        if (!cpu->getInstPort().sendTiming(data_pkt)) {
+        if (!cpu->getInstPort().sendTimingReq(data_pkt)) {
             assert(retryPkt == NULL);
             assert(retryTid == InvalidThreadID);
             DPRINTF(Fetch, "[tid:%i] Out of MSHRs!\n", tid);
@@ -1356,7 +1356,7 @@ DefaultFetch<Impl>::recvRetry()
         assert(retryTid != InvalidThreadID);
         assert(fetchStatus[retryTid] == IcacheWaitRetry);
 
-        if (cpu->getInstPort().sendTiming(retryPkt)) {
+        if (cpu->getInstPort().sendTimingReq(retryPkt)) {
             fetchStatus[retryTid] = IcacheWaitResponse;
             retryPkt = NULL;
             retryTid = InvalidThreadID;
diff --git a/src/cpu/o3/lsq.hh b/src/cpu/o3/lsq.hh
index dac5fab18..026033539 100644
--- a/src/cpu/o3/lsq.hh
+++ b/src/cpu/o3/lsq.hh
@@ -297,9 +297,9 @@ class LSQ {
      *
      * @param pkt Response packet from the memory sub-system
      */
-    bool recvTiming(PacketPtr pkt);
+    bool recvTimingResp(PacketPtr pkt);
 
-    bool recvTimingSnoop(PacketPtr pkt);
+    void recvTimingSnoopReq(PacketPtr pkt);
 
     /** The CPU pointer. */
     O3CPU *cpu;
diff --git a/src/cpu/o3/lsq_impl.hh b/src/cpu/o3/lsq_impl.hh
index c2f410e37..72ffdd58b 100644
--- a/src/cpu/o3/lsq_impl.hh
+++ b/src/cpu/o3/lsq_impl.hh
@@ -319,9 +319,8 @@ LSQ<Impl>::recvRetry()
 
 template <class Impl>
 bool
-LSQ<Impl>::recvTiming(PacketPtr pkt)
+LSQ<Impl>::recvTimingResp(PacketPtr pkt)
 {
-    assert(pkt->isResponse());
     if (pkt->isError())
         DPRINTF(LSQ, "Got error packet back for address: %#X\n",
                 pkt->getAddr());
@@ -330,10 +329,9 @@ LSQ<Impl>::recvTiming(PacketPtr pkt)
 }
 
 template <class Impl>
-bool
-LSQ<Impl>::recvTimingSnoop(PacketPtr pkt)
+void
+LSQ<Impl>::recvTimingSnoopReq(PacketPtr pkt)
 {
-    assert(pkt->isRequest());
     DPRINTF(LSQ, "received pkt for addr:%#x %s\n", pkt->getAddr(),
             pkt->cmdString());
 
@@ -345,9 +343,6 @@ LSQ<Impl>::recvTimingSnoop(PacketPtr pkt)
             thread[tid].checkSnoop(pkt);
         }
     }
-
-    // to provide stronger consistency model
-    return true;
 }
 
 template<class Impl>
diff --git a/src/cpu/o3/lsq_unit.hh b/src/cpu/o3/lsq_unit.hh
index 44c3df0bf..ad1e26d2f 100644
--- a/src/cpu/o3/lsq_unit.hh
+++ b/src/cpu/o3/lsq_unit.hh
@@ -801,7 +801,7 @@ LSQUnit<Impl>::read(Request *req, Request *sreqLow, Request *sreqHigh,
             state->mainPkt = data_pkt;
         }
 
-        if (!dcachePort->sendTiming(fst_data_pkt)) {
+        if (!dcachePort->sendTimingReq(fst_data_pkt)) {
             // Delete state and data packet because a load retry
             // initiates a pipeline restart; it does not retry.
             delete state;
@@ -830,7 +830,7 @@ LSQUnit<Impl>::read(Request *req, Request *sreqLow, Request *sreqHigh,
             // The first packet will return in completeDataAccess and be
             // handled there.
             ++usedPorts;
-            if (!dcachePort->sendTiming(snd_data_pkt)) {
+            if (!dcachePort->sendTimingReq(snd_data_pkt)) {
 
                 // The main packet will be deleted in completeDataAccess.
                 delete snd_data_pkt->req;
diff --git a/src/cpu/o3/lsq_unit_impl.hh b/src/cpu/o3/lsq_unit_impl.hh
index f4182e30d..4f82ad9e3 100644
--- a/src/cpu/o3/lsq_unit_impl.hh
+++ b/src/cpu/o3/lsq_unit_impl.hh
@@ -1180,7 +1180,7 @@ template <class Impl>
 bool
 LSQUnit<Impl>::sendStore(PacketPtr data_pkt)
 {
-    if (!dcachePort->sendTiming(data_pkt)) {
+    if (!dcachePort->sendTimingReq(data_pkt)) {
         // Need to handle becoming blocked on a store.
         isStoreBlocked = true;
         ++lsqCacheBlocked;
@@ -1203,7 +1203,7 @@ LSQUnit<Impl>::recvRetry()
         LSQSenderState *state =
             dynamic_cast<LSQSenderState *>(retryPkt->senderState);
 
-        if (dcachePort->sendTiming(retryPkt)) {
+        if (dcachePort->sendTimingReq(retryPkt)) {
             // Don't finish the store unless this is the last packet.
             if (!TheISA::HasUnalignedMemAcc || !state->pktToSend ||
                     state->pendingPacket == retryPkt) {
diff --git a/src/cpu/simple/timing.cc b/src/cpu/simple/timing.cc
index 5dba51842..3d771e56b 100644
--- a/src/cpu/simple/timing.cc
+++ b/src/cpu/simple/timing.cc
@@ -234,7 +234,7 @@ TimingSimpleCPU::handleReadPacket(PacketPtr pkt)
         new IprEvent(pkt, this, nextCycle(curTick() + delay));
         _status = DcacheWaitResponse;
         dcache_pkt = NULL;
-    } else if (!dcachePort.sendTiming(pkt)) {
+    } else if (!dcachePort.sendTimingReq(pkt)) {
         _status = DcacheRetry;
         dcache_pkt = pkt;
     } else {
@@ -449,7 +449,7 @@ TimingSimpleCPU::handleWritePacket()
         new IprEvent(dcache_pkt, this, nextCycle(curTick() + delay));
         _status = DcacheWaitResponse;
         dcache_pkt = NULL;
-    } else if (!dcachePort.sendTiming(dcache_pkt)) {
+    } else if (!dcachePort.sendTimingReq(dcache_pkt)) {
         _status = DcacheRetry;
     } else {
         _status = DcacheWaitResponse;
@@ -581,7 +581,7 @@ TimingSimpleCPU::sendFetch(Fault fault, RequestPtr req, ThreadContext *tc)
         ifetch_pkt->dataStatic(&inst);
         DPRINTF(SimpleCPU, " -- pkt addr: %#x\n", ifetch_pkt->getAddr());
 
-        if (!icachePort.sendTiming(ifetch_pkt)) {
+        if (!icachePort.sendTimingReq(ifetch_pkt)) {
             // Need to wait for retry
             _status = IcacheRetry;
         } else {
@@ -715,9 +715,8 @@ TimingSimpleCPU::IcachePort::ITickEvent::process()
 }
 
 bool
-TimingSimpleCPU::IcachePort::recvTiming(PacketPtr pkt)
+TimingSimpleCPU::IcachePort::recvTimingResp(PacketPtr pkt)
 {
-    assert(pkt->isResponse());
     if (!pkt->wasNacked()) {
         DPRINTF(SimpleCPU, "Received timing response %#x\n", pkt->getAddr());
         // delay processing of returned data until next CPU clock edge
@@ -732,7 +731,7 @@ TimingSimpleCPU::IcachePort::recvTiming(PacketPtr pkt)
     } else {
         assert(cpu->_status == IcacheWaitResponse);
         pkt->reinitNacked();
-        if (!sendTiming(pkt)) {
+        if (!sendTimingReq(pkt)) {
             cpu->_status = IcacheRetry;
             cpu->ifetch_pkt = pkt;
         }
@@ -749,7 +748,7 @@ TimingSimpleCPU::IcachePort::recvRetry()
     assert(cpu->ifetch_pkt != NULL);
     assert(cpu->_status == IcacheRetry);
     PacketPtr tmp = cpu->ifetch_pkt;
-    if (sendTiming(tmp)) {
+    if (sendTimingReq(tmp)) {
         cpu->_status = IcacheWaitResponse;
         cpu->ifetch_pkt = NULL;
     }
@@ -836,9 +835,8 @@ TimingSimpleCPU::completeDrain()
 }
 
 bool
-TimingSimpleCPU::DcachePort::recvTiming(PacketPtr pkt)
+TimingSimpleCPU::DcachePort::recvTimingResp(PacketPtr pkt)
 {
-    assert(pkt->isResponse());
     if (!pkt->wasNacked()) {
         // delay processing of returned data until next CPU clock edge
         Tick next_tick = cpu->nextCycle(curTick());
@@ -862,7 +860,7 @@ TimingSimpleCPU::DcachePort::recvTiming(PacketPtr pkt)
     } else  {
         assert(cpu->_status == DcacheWaitResponse);
         pkt->reinitNacked();
-        if (!sendTiming(pkt)) {
+        if (!sendTimingReq(pkt)) {
             cpu->_status = DcacheRetry;
             cpu->dcache_pkt = pkt;
         }
@@ -896,7 +894,7 @@ TimingSimpleCPU::DcachePort::recvRetry()
             dynamic_cast<SplitMainSenderState *>(big_pkt->senderState);
         assert(main_send_state);
 
-        if (sendTiming(tmp)) {
+        if (sendTimingReq(tmp)) {
             // If we were able to send without retrying, record that fact
             // and try sending the other fragment.
             send_state->clearFromParent();
@@ -914,7 +912,7 @@ TimingSimpleCPU::DcachePort::recvRetry()
                 cpu->dcache_pkt = NULL;
             }
         }
-    } else if (sendTiming(tmp)) {
+    } else if (sendTimingReq(tmp)) {
         cpu->_status = DcacheWaitResponse;
         // memory system takes ownership of packet
         cpu->dcache_pkt = NULL;
diff --git a/src/cpu/simple/timing.hh b/src/cpu/simple/timing.hh
index 4c23391d9..16bb554e2 100644
--- a/src/cpu/simple/timing.hh
+++ b/src/cpu/simple/timing.hh
@@ -156,7 +156,7 @@ class TimingSimpleCPU : public BaseSimpleCPU
         /**
          * Snooping a coherence request, do nothing.
          */
-        virtual bool recvTimingSnoop(PacketPtr pkt) { return true; }
+        virtual void recvTimingSnoopReq(PacketPtr pkt) { }
 
         TimingSimpleCPU* cpu;
 
@@ -185,7 +185,7 @@ class TimingSimpleCPU : public BaseSimpleCPU
 
       protected:
 
-        virtual bool recvTiming(PacketPtr pkt);
+        virtual bool recvTimingResp(PacketPtr pkt);
 
         virtual void recvRetry();
 
@@ -212,7 +212,7 @@ class TimingSimpleCPU : public BaseSimpleCPU
 
       protected:
 
-        virtual bool recvTiming(PacketPtr pkt);
+        virtual bool recvTimingResp(PacketPtr pkt);
 
         virtual void recvRetry();
 
diff --git a/src/cpu/testers/directedtest/InvalidateGenerator.cc b/src/cpu/testers/directedtest/InvalidateGenerator.cc
index a89853061..84a90844f 100644
--- a/src/cpu/testers/directedtest/InvalidateGenerator.cc
+++ b/src/cpu/testers/directedtest/InvalidateGenerator.cc
@@ -80,7 +80,7 @@ InvalidateGenerator::initiate()
     *dummyData = 0;
     pkt->dataDynamic(dummyData);
 
-    if (port->sendTiming(pkt)) {
+    if (port->sendTimingReq(pkt)) {
         DPRINTF(DirectedTest, "initiating request - successful\n");
         if (m_status == InvalidateGeneratorStatus_Load_Waiting) {
             m_status = InvalidateGeneratorStatus_Load_Pending;
diff --git a/src/cpu/testers/directedtest/RubyDirectedTester.cc b/src/cpu/testers/directedtest/RubyDirectedTester.cc
index b5fe662af..0aba82dd2 100644
--- a/src/cpu/testers/directedtest/RubyDirectedTester.cc
+++ b/src/cpu/testers/directedtest/RubyDirectedTester.cc
@@ -91,7 +91,7 @@ RubyDirectedTester::getMasterPort(const std::string &if_name, int idx)
 }
 
 bool
-RubyDirectedTester::CpuPort::recvTiming(PacketPtr pkt)
+RubyDirectedTester::CpuPort::recvTimingResp(PacketPtr pkt)
 {
     tester->hitCallback(id, pkt->getAddr());
     
diff --git a/src/cpu/testers/directedtest/RubyDirectedTester.hh b/src/cpu/testers/directedtest/RubyDirectedTester.hh
index 08b034d3f..75e72edf8 100644
--- a/src/cpu/testers/directedtest/RubyDirectedTester.hh
+++ b/src/cpu/testers/directedtest/RubyDirectedTester.hh
@@ -59,7 +59,7 @@ class RubyDirectedTester : public MemObject
         {}
 
       protected:
-        virtual bool recvTiming(PacketPtr pkt);
+        virtual bool recvTimingResp(PacketPtr pkt);
         virtual void recvRetry()
         { panic("%s does not expect a retry\n", name()); }
     };
diff --git a/src/cpu/testers/directedtest/SeriesRequestGenerator.cc b/src/cpu/testers/directedtest/SeriesRequestGenerator.cc
index b8c42b67d..abcb0278f 100644
--- a/src/cpu/testers/directedtest/SeriesRequestGenerator.cc
+++ b/src/cpu/testers/directedtest/SeriesRequestGenerator.cc
@@ -70,7 +70,7 @@ SeriesRequestGenerator::initiate()
     *dummyData = 0;
     pkt->dataDynamic(dummyData);
 
-    if (port->sendTiming(pkt)) {
+    if (port->sendTimingReq(pkt)) {
         DPRINTF(DirectedTest, "initiating request - successful\n");
         m_status = SeriesRequestGeneratorStatus_Request_Pending;
         return true;
diff --git a/src/cpu/testers/memtest/memtest.cc b/src/cpu/testers/memtest/memtest.cc
index 809b4dd93..642af4677 100644
--- a/src/cpu/testers/memtest/memtest.cc
+++ b/src/cpu/testers/memtest/memtest.cc
@@ -53,9 +53,8 @@ using namespace std;
 int TESTER_ALLOCATOR=0;
 
 bool
-MemTest::CpuPort::recvTiming(PacketPtr pkt)
+MemTest::CpuPort::recvTimingResp(PacketPtr pkt)
 {
-    assert(pkt->isResponse());
     memtest->completeRequest(pkt);
     return true;
 }
@@ -72,7 +71,7 @@ MemTest::sendPkt(PacketPtr pkt) {
         cachePort.sendAtomic(pkt);
         completeRequest(pkt);
     }
-    else if (!cachePort.sendTiming(pkt)) {
+    else if (!cachePort.sendTimingReq(pkt)) {
         DPRINTF(MemTest, "accessRetry setting to true\n");
 
         //
@@ -379,7 +378,7 @@ MemTest::tick()
 void
 MemTest::doRetry()
 {
-    if (cachePort.sendTiming(retryPkt)) {
+    if (cachePort.sendTimingReq(retryPkt)) {
         DPRINTF(MemTest, "accessRetry setting to false\n");
         accessRetry = false;
         retryPkt = NULL;
diff --git a/src/cpu/testers/memtest/memtest.hh b/src/cpu/testers/memtest/memtest.hh
index 8dccfdc80..450a3e4f1 100644
--- a/src/cpu/testers/memtest/memtest.hh
+++ b/src/cpu/testers/memtest/memtest.hh
@@ -97,9 +97,9 @@ class MemTest : public MemObject
 
       protected:
 
-        virtual bool recvTiming(PacketPtr pkt);
+        virtual bool recvTimingResp(PacketPtr pkt);
 
-        virtual bool recvTimingSnoop(PacketPtr pkt) { return true; }
+        virtual void recvTimingSnoopReq(PacketPtr pkt) { }
 
         virtual Tick recvAtomicSnoop(PacketPtr pkt) { return 0; }
 
diff --git a/src/cpu/testers/networktest/networktest.cc b/src/cpu/testers/networktest/networktest.cc
index aa8b54b8e..5d0e8e0c9 100644
--- a/src/cpu/testers/networktest/networktest.cc
+++ b/src/cpu/testers/networktest/networktest.cc
@@ -51,9 +51,8 @@ using namespace std;
 int TESTER_NETWORK=0;
 
 bool
-NetworkTest::CpuPort::recvTiming(PacketPtr pkt)
+NetworkTest::CpuPort::recvTimingResp(PacketPtr pkt)
 {
-    assert(pkt->isResponse());
     networktest->completeRequest(pkt);
     return true;
 }
@@ -67,7 +66,7 @@ NetworkTest::CpuPort::recvRetry()
 void
 NetworkTest::sendPkt(PacketPtr pkt)
 {
-    if (!cachePort.sendTiming(pkt)) {
+    if (!cachePort.sendTimingReq(pkt)) {
         retryPkt = pkt; // RubyPort will retry sending
     }
     numPacketsSent++;
@@ -269,7 +268,7 @@ NetworkTest::generatePkt()
 void
 NetworkTest::doRetry()
 {
-    if (cachePort.sendTiming(retryPkt)) {
+    if (cachePort.sendTimingReq(retryPkt)) {
         retryPkt = NULL;
     }
 }
diff --git a/src/cpu/testers/networktest/networktest.hh b/src/cpu/testers/networktest/networktest.hh
index 36d311aa8..8b7a89d6f 100644
--- a/src/cpu/testers/networktest/networktest.hh
+++ b/src/cpu/testers/networktest/networktest.hh
@@ -92,7 +92,7 @@ class NetworkTest : public MemObject
 
       protected:
 
-        virtual bool recvTiming(PacketPtr pkt);
+        virtual bool recvTimingResp(PacketPtr pkt);
 
         virtual void recvRetry();
     };
diff --git a/src/cpu/testers/rubytest/Check.cc b/src/cpu/testers/rubytest/Check.cc
index 8188fecbb..98250f042 100644
--- a/src/cpu/testers/rubytest/Check.cc
+++ b/src/cpu/testers/rubytest/Check.cc
@@ -114,7 +114,7 @@ Check::initiatePrefetch()
     pkt->senderState =
         new SenderState(m_address, req->getSize(), pkt->senderState);
 
-    if (port->sendTiming(pkt)) {
+    if (port->sendTimingReq(pkt)) {
         DPRINTF(RubyTest, "successfully initiated prefetch.\n");
     } else {
         // If the packet did not issue, must delete
@@ -154,7 +154,7 @@ Check::initiateFlush()
     pkt->senderState =
         new SenderState(m_address, req->getSize(), pkt->senderState);
 
-    if (port->sendTiming(pkt)) {
+    if (port->sendTimingReq(pkt)) {
         DPRINTF(RubyTest, "initiating Flush - successful\n");
     }
 }
@@ -201,7 +201,7 @@ Check::initiateAction()
     pkt->senderState =
         new SenderState(writeAddr, req->getSize(), pkt->senderState);
 
-    if (port->sendTiming(pkt)) {
+    if (port->sendTimingReq(pkt)) {
         DPRINTF(RubyTest, "initiating action - successful\n");
         DPRINTF(RubyTest, "status before action update: %s\n",
                 (TesterStatus_to_string(m_status)).c_str());
@@ -253,7 +253,7 @@ Check::initiateCheck()
     pkt->senderState =
         new SenderState(m_address, req->getSize(), pkt->senderState);
 
-    if (port->sendTiming(pkt)) {
+    if (port->sendTimingReq(pkt)) {
         DPRINTF(RubyTest, "initiating check - successful\n");
         DPRINTF(RubyTest, "status before check update: %s\n",
                 TesterStatus_to_string(m_status).c_str());
diff --git a/src/cpu/testers/rubytest/RubyTester.cc b/src/cpu/testers/rubytest/RubyTester.cc
index 2862a261d..3397b00d0 100644
--- a/src/cpu/testers/rubytest/RubyTester.cc
+++ b/src/cpu/testers/rubytest/RubyTester.cc
@@ -145,7 +145,7 @@ RubyTester::getMasterPort(const std::string &if_name, int idx)
 }
 
 bool
-RubyTester::CpuPort::recvTiming(PacketPtr pkt)
+RubyTester::CpuPort::recvTimingResp(PacketPtr pkt)
 {
     // retrieve the subblock and call hitCallback
     RubyTester::SenderState* senderState =
diff --git a/src/cpu/testers/rubytest/RubyTester.hh b/src/cpu/testers/rubytest/RubyTester.hh
index 5d2202f65..8fbd886b3 100644
--- a/src/cpu/testers/rubytest/RubyTester.hh
+++ b/src/cpu/testers/rubytest/RubyTester.hh
@@ -62,7 +62,7 @@ class RubyTester : public MemObject
         {}
 
       protected:
-        virtual bool recvTiming(PacketPtr pkt);
+        virtual bool recvTimingResp(PacketPtr pkt);
         virtual void recvRetry()
         { panic("%s does not expect a retry\n", name()); }
     };
diff --git a/src/dev/io_device.cc b/src/dev/io_device.cc
index 5fadb2f49..eb799f688 100644
--- a/src/dev/io_device.cc
+++ b/src/dev/io_device.cc
@@ -131,9 +131,8 @@ DmaPort::DmaPort(MemObject *dev, System *s, Tick min_backoff, Tick max_backoff,
 { }
 
 bool
-DmaPort::recvTiming(PacketPtr pkt)
+DmaPort::recvTimingResp(PacketPtr pkt)
 {
-    assert(pkt->isResponse());
     if (pkt->wasNacked()) {
         DPRINTF(DMA, "Received nacked %s addr %#x\n",
                 pkt->cmdString(), pkt->getAddr());
@@ -234,7 +233,7 @@ DmaPort::recvRetry()
         PacketPtr pkt = transmitList.front();
         DPRINTF(DMA, "Retry on %s addr %#x\n",
                 pkt->cmdString(), pkt->getAddr());
-        result = sendTiming(pkt);
+        result = sendTimingReq(pkt);
         if (result) {
             DPRINTF(DMA, "-- Done\n");
             transmitList.pop_front();
@@ -320,7 +319,7 @@ DmaPort::sendDma()
 
         bool result;
         do {
-            result = sendTiming(pkt);
+            result = sendTimingReq(pkt);
             if (result) {
                 transmitList.pop_front();
                 DPRINTF(DMA, "-- Done\n");
diff --git a/src/dev/io_device.hh b/src/dev/io_device.hh
index b113f4379..99b207595 100644
--- a/src/dev/io_device.hh
+++ b/src/dev/io_device.hh
@@ -146,13 +146,12 @@ class DmaPort : public MasterPort
     /** Port accesses a cache which requires snooping */
     bool recvSnoops;
 
-    virtual bool recvTiming(PacketPtr pkt);
+    virtual bool recvTimingResp(PacketPtr pkt);
 
-    virtual bool recvTimingSnoop(PacketPtr pkt)
+    virtual void recvTimingSnoopReq(PacketPtr pkt)
     {
         if (!recvSnoops)
             panic("%s was not expecting a snoop\n", name());
-        return true;
     }
 
     virtual Tick recvAtomicSnoop(PacketPtr pkt)
diff --git a/src/mem/bridge.cc b/src/mem/bridge.cc
index ddbc154c0..15b41b5ef 100644
--- a/src/mem/bridge.cc
+++ b/src/mem/bridge.cc
@@ -137,11 +137,8 @@ Bridge::BridgeMasterPort::reqQueueFull()
 }
 
 bool
-Bridge::BridgeMasterPort::recvTiming(PacketPtr pkt)
+Bridge::BridgeMasterPort::recvTimingResp(PacketPtr pkt)
 {
-    // should only see responses on the master side
-    assert(pkt->isResponse());
-
     // all checks are done when the request is accepted on the slave
     // side, so we are guaranteed to have space for the response
     DPRINTF(BusBridge, "recvTiming: response %s addr 0x%x\n",
@@ -155,12 +152,8 @@ Bridge::BridgeMasterPort::recvTiming(PacketPtr pkt)
 }
 
 bool
-Bridge::BridgeSlavePort::recvTiming(PacketPtr pkt)
+Bridge::BridgeSlavePort::recvTimingReq(PacketPtr pkt)
 {
-    // should only see requests on the slave side
-    assert(pkt->isRequest());
-
-
     DPRINTF(BusBridge, "recvTiming: request %s addr 0x%x\n",
             pkt->cmdString(), pkt->getAddr());
 
@@ -318,7 +311,7 @@ Bridge::BridgeMasterPort::trySend()
     if (!buf->expectResponse)
         pkt->senderState = NULL;
 
-    if (sendTiming(pkt)) {
+    if (sendTimingReq(pkt)) {
         // send successful
         requestQueue.pop_front();
         // we no longer own packet, so it's not safe to look at it
@@ -365,7 +358,7 @@ Bridge::BridgeSlavePort::trySend()
     // no need to worry about the sender state since we are not
     // modifying it
 
-    if (sendTiming(pkt)) {
+    if (sendTimingResp(pkt)) {
         DPRINTF(BusBridge, "  successful\n");
         // send successful
         responseQueue.pop_front();
diff --git a/src/mem/bridge.hh b/src/mem/bridge.hh
index 45c7e3057..d7bed9605 100644
--- a/src/mem/bridge.hh
+++ b/src/mem/bridge.hh
@@ -230,7 +230,7 @@ class Bridge : public MemObject
 
         /** When receiving a timing request from the peer port,
             pass it to the bridge. */
-        virtual bool recvTiming(PacketPtr pkt);
+        virtual bool recvTimingReq(PacketPtr pkt);
 
         /** When receiving a retry request from the peer port,
             pass it to the bridge. */
@@ -353,7 +353,7 @@ class Bridge : public MemObject
 
         /** When receiving a timing request from the peer port,
             pass it to the bridge. */
-        virtual bool recvTiming(PacketPtr pkt);
+        virtual bool recvTimingResp(PacketPtr pkt);
 
         /** When receiving a retry request from the peer port,
             pass it to the bridge. */
diff --git a/src/mem/bus.cc b/src/mem/bus.cc
index 911276f75..61b84d82e 100644
--- a/src/mem/bus.cc
+++ b/src/mem/bus.cc
@@ -198,186 +198,199 @@ Bus::isOccupied(PacketPtr pkt, Port* port)
 }
 
 bool
-Bus::recvTiming(PacketPtr pkt)
+Bus::recvTimingReq(PacketPtr pkt)
 {
-    // get the source id
-    Packet::NodeID src_id = pkt->getSrc();
-
-    // determine the source port based on the id and direction
-    Port *src_port = NULL;
-    if (pkt->isRequest())
-        src_port = slavePorts[src_id];
-    else
-        src_port = masterPorts[src_id];
+    // determine the source port based on the id
+    SlavePort *src_port = slavePorts[pkt->getSrc()];
 
     // test if the bus should be considered occupied for the current
     // packet, and exclude express snoops from the check
     if (!pkt->isExpressSnoop() && isOccupied(pkt, src_port)) {
-        DPRINTF(Bus, "recvTiming: src %s %s 0x%x BUSY\n",
+        DPRINTF(Bus, "recvTimingReq: src %s %s 0x%x BUSY\n",
                 src_port->name(), pkt->cmdString(), pkt->getAddr());
         return false;
     }
 
-    DPRINTF(Bus, "recvTiming: src %s %s 0x%x\n",
+    DPRINTF(Bus, "recvTimingReq: src %s %s 0x%x\n",
             src_port->name(), pkt->cmdString(), pkt->getAddr());
 
     Tick headerFinishTime = pkt->isExpressSnoop() ? 0 : calcPacketTiming(pkt);
     Tick packetFinishTime = pkt->isExpressSnoop() ? 0 : pkt->finishTime;
 
-    // decide what to do based on the direction
-    if (pkt->isRequest()) {
-        // the packet is a memory-mapped request and should be
-        // broadcasted to our snoopers but the source
-        forwardTiming(pkt, src_id);
-
-        // remember if we add an outstanding req so we can undo it if
-        // necessary, if the packet needs a response, we should add it
-        // as outstanding and express snoops never fail so there is
-        // not need to worry about them
-        bool add_outstanding = !pkt->isExpressSnoop() && pkt->needsResponse();
-
-        // keep track that we have an outstanding request packet
-        // matching this request, this is used by the coherency
-        // mechanism in determining what to do with snoop responses
-        // (in recvTimingSnoop)
-        if (add_outstanding) {
-            // we should never have an exsiting request outstanding
-            assert(outstandingReq.find(pkt->req) == outstandingReq.end());
-            outstandingReq.insert(pkt->req);
-        }
+    // the packet is a memory-mapped request and should be
+    // broadcasted to our snoopers but the source
+    forwardTiming(pkt, pkt->getSrc());
+
+    // remember if we add an outstanding req so we can undo it if
+    // necessary, if the packet needs a response, we should add it
+    // as outstanding and express snoops never fail so there is
+    // not need to worry about them
+    bool add_outstanding = !pkt->isExpressSnoop() && pkt->needsResponse();
+
+    // keep track that we have an outstanding request packet
+    // matching this request, this is used by the coherency
+    // mechanism in determining what to do with snoop responses
+    // (in recvTimingSnoop)
+    if (add_outstanding) {
+        // we should never have an exsiting request outstanding
+        assert(outstandingReq.find(pkt->req) == outstandingReq.end());
+        outstandingReq.insert(pkt->req);
+    }
+
+    // since it is a normal request, determine the destination
+    // based on the address and attempt to send the packet
+    bool success = masterPorts[findPort(pkt->getAddr())]->sendTimingReq(pkt);
+
+    if (!success)  {
+        // inhibited packets should never be forced to retry
+        assert(!pkt->memInhibitAsserted());
+
+        // if it was added as outstanding and the send failed, then
+        // erase it again
+        if (add_outstanding)
+            outstandingReq.erase(pkt->req);
 
-        // since it is a normal request, determine the destination
-        // based on the address and attempt to send the packet
-        bool success = masterPorts[findPort(pkt->getAddr())]->sendTiming(pkt);
+        DPRINTF(Bus, "recvTimingReq: src %s %s 0x%x RETRY\n",
+                src_port->name(), pkt->cmdString(), pkt->getAddr());
 
-        if (!success)  {
-            // inhibited packets should never be forced to retry
-            assert(!pkt->memInhibitAsserted());
+        addToRetryList(src_port);
+        occupyBus(headerFinishTime);
 
-            // if it was added as outstanding and the send failed, then
-            // erase it again
-            if (add_outstanding)
-                outstandingReq.erase(pkt->req);
+        return false;
+    }
 
-            DPRINTF(Bus, "recvTiming: src %s %s 0x%x RETRY\n",
-                    src_port->name(), pkt->cmdString(), pkt->getAddr());
+    succeededTiming(packetFinishTime);
 
-            addToRetryList(src_port);
-            occupyBus(headerFinishTime);
+    return true;
+}
 
-            return false;
-        }
-    } else {
-        // the packet is a normal response to a request that we should
-        // have seen passing through the bus
-        assert(outstandingReq.find(pkt->req) != outstandingReq.end());
+bool
+Bus::recvTimingResp(PacketPtr pkt)
+{
+    // determine the source port based on the id
+    MasterPort *src_port = masterPorts[pkt->getSrc()];
 
-        // remove it as outstanding
-        outstandingReq.erase(pkt->req);
+    // test if the bus should be considered occupied for the current
+    // packet
+    if (isOccupied(pkt, src_port)) {
+        DPRINTF(Bus, "recvTimingResp: src %s %s 0x%x BUSY\n",
+                src_port->name(), pkt->cmdString(), pkt->getAddr());
+        return false;
+    }
 
-        // send the packet to the destination through one of our slave
-        // ports, as determined by the destination field
-        bool success M5_VAR_USED = slavePorts[pkt->getDest()]->sendTiming(pkt);
+    DPRINTF(Bus, "recvTimingResp: src %s %s 0x%x\n",
+            src_port->name(), pkt->cmdString(), pkt->getAddr());
 
-        // currently it is illegal to block responses... can lead to
-        // deadlock
-        assert(success);
-    }
+    calcPacketTiming(pkt);
+    Tick packetFinishTime = pkt->finishTime;
+
+    // the packet is a normal response to a request that we should
+    // have seen passing through the bus
+    assert(outstandingReq.find(pkt->req) != outstandingReq.end());
+
+    // remove it as outstanding
+    outstandingReq.erase(pkt->req);
+
+    // send the packet to the destination through one of our slave
+    // ports, as determined by the destination field
+    bool success M5_VAR_USED = slavePorts[pkt->getDest()]->sendTimingResp(pkt);
+
+    // currently it is illegal to block responses... can lead to
+    // deadlock
+    assert(success);
 
     succeededTiming(packetFinishTime);
 
     return true;
 }
 
-bool
-Bus::recvTimingSnoop(PacketPtr pkt)
+void
+Bus::recvTimingSnoopReq(PacketPtr pkt)
 {
-    // get the source id
-    Packet::NodeID src_id = pkt->getSrc();
+    DPRINTF(Bus, "recvTimingSnoopReq: src %s %s 0x%x\n",
+            masterPorts[pkt->getSrc()]->name(), pkt->cmdString(),
+            pkt->getAddr());
 
-    if (pkt->isRequest()) {
-        DPRINTF(Bus, "recvTimingSnoop: src %d %s 0x%x\n",
-                src_id, pkt->cmdString(), pkt->getAddr());
+    // we should only see express snoops from caches
+    assert(pkt->isExpressSnoop());
 
-        // the packet is an express snoop request and should be
-        // broadcasted to our snoopers
-        assert(pkt->isExpressSnoop());
+    // forward to all snoopers
+    forwardTiming(pkt, Port::INVALID_PORT_ID);
 
-        // forward to all snoopers
-        forwardTiming(pkt, Port::INVALID_PORT_ID);
+    // a snoop request came from a connected slave device (one of
+    // our master ports), and if it is not coming from the slave
+    // device responsible for the address range something is
+    // wrong, hence there is nothing further to do as the packet
+    // would be going back to where it came from
+    assert(pkt->getSrc() == findPort(pkt->getAddr()));
 
-        // a snoop request came from a connected slave device (one of
-        // our master ports), and if it is not coming from the slave
-        // device responsible for the address range something is
-        // wrong, hence there is nothing further to do as the packet
-        // would be going back to where it came from
-        assert(src_id == findPort(pkt->getAddr()));
+    // this is an express snoop and is never forced to retry
+    assert(!inRetry);
+}
 
-        // this is an express snoop and is never forced to retry
-        assert(!inRetry);
+bool
+Bus::recvTimingSnoopResp(PacketPtr pkt)
+{
+    // determine the source port based on the id
+    SlavePort* src_port = slavePorts[pkt->getSrc()];
 
-        return true;
-    } else {
-        // determine the source port based on the id
-        SlavePort* src_port = slavePorts[src_id];
+    if (isOccupied(pkt, src_port)) {
+        DPRINTF(Bus, "recvTimingSnoopResp: src %s %s 0x%x BUSY\n",
+                src_port->name(), pkt->cmdString(), pkt->getAddr());
+        return false;
+    }
 
-        if (isOccupied(pkt, src_port)) {
-            DPRINTF(Bus, "recvTimingSnoop: src %s %s 0x%x BUSY\n",
-                    src_port->name(), pkt->cmdString(), pkt->getAddr());
-            return false;
-        }
+    DPRINTF(Bus, "recvTimingSnoop: src %s %s 0x%x\n",
+            src_port->name(), pkt->cmdString(), pkt->getAddr());
 
-        DPRINTF(Bus, "recvTimingSnoop: src %s %s 0x%x\n",
-                src_port->name(), pkt->cmdString(), pkt->getAddr());
+    // get the destination from the packet
+    Packet::NodeID dest = pkt->getDest();
 
-        // get the destination from the packet
-        Packet::NodeID dest = pkt->getDest();
-
-        // responses are never express snoops
-        assert(!pkt->isExpressSnoop());
-
-        calcPacketTiming(pkt);
-        Tick packetFinishTime = pkt->finishTime;
-
-        // determine if the response is from a snoop request we
-        // created as the result of a normal request (in which case it
-        // should be in the outstandingReq), or if we merely forwarded
-        // someone else's snoop request
-        if (outstandingReq.find(pkt->req) == outstandingReq.end()) {
-            // this is a snoop response to a snoop request we
-            // forwarded, e.g. coming from the L1 and going to the L2
-            // this should be forwarded as a snoop response
-            bool success M5_VAR_USED = masterPorts[dest]->sendTimingSnoop(pkt);
-            assert(success);
-        } else {
-            // we got a snoop response on one of our slave ports,
-            // i.e. from a coherent master connected to the bus, and
-            // since we created the snoop request as part of
-            // recvTiming, this should now be a normal response again
-            outstandingReq.erase(pkt->req);
+    // responses are never express snoops
+    assert(!pkt->isExpressSnoop());
 
-            // this is a snoop response from a coherent master, with a
-            // destination field set on its way through the bus as
-            // request, hence it should never go back to where the
-            // snoop response came from, but instead to where the
-            // original request came from
-            assert(src_id != dest);
+    calcPacketTiming(pkt);
+    Tick packetFinishTime = pkt->finishTime;
 
-            // as a normal response, it should go back to a master
-            // through one of our slave ports
-            bool success M5_VAR_USED = slavePorts[dest]->sendTiming(pkt);
+    // determine if the response is from a snoop request we
+    // created as the result of a normal request (in which case it
+    // should be in the outstandingReq), or if we merely forwarded
+    // someone else's snoop request
+    if (outstandingReq.find(pkt->req) == outstandingReq.end()) {
+        // this is a snoop response to a snoop request we
+        // forwarded, e.g. coming from the L1 and going to the L2
+        // this should be forwarded as a snoop response
+        bool success M5_VAR_USED = masterPorts[dest]->sendTimingSnoopResp(pkt);
+        assert(success);
+    } else {
+        // we got a snoop response on one of our slave ports,
+        // i.e. from a coherent master connected to the bus, and
+        // since we created the snoop request as part of
+        // recvTiming, this should now be a normal response again
+        outstandingReq.erase(pkt->req);
 
-            // currently it is illegal to block responses... can lead
-            // to deadlock
-            assert(success);
-        }
+        // this is a snoop response from a coherent master, with a
+        // destination field set on its way through the bus as
+        // request, hence it should never go back to where the
+        // snoop response came from, but instead to where the
+        // original request came from
+        assert(pkt->getSrc() != dest);
 
-        succeededTiming(packetFinishTime);
+        // as a normal response, it should go back to a master
+        // through one of our slave ports
+        bool success M5_VAR_USED = slavePorts[dest]->sendTimingResp(pkt);
 
-        return true;
+        // currently it is illegal to block responses... can lead
+        // to deadlock
+        assert(success);
     }
+
+    succeededTiming(packetFinishTime);
+
+    return true;
 }
 
+
 void
 Bus::succeededTiming(Tick busy_time)
 {
@@ -405,8 +418,7 @@ Bus::forwardTiming(PacketPtr pkt, int exclude_slave_port_id)
         if (exclude_slave_port_id == Port::INVALID_PORT_ID ||
             p->getId() != exclude_slave_port_id) {
             // cache is not allowed to refuse snoop
-            bool success M5_VAR_USED = p->sendTimingSnoop(pkt);
-            assert(success);
+            p->sendTimingSnoopReq(pkt);
         }
     }
 }
@@ -531,9 +543,6 @@ Bus::recvAtomic(PacketPtr pkt)
             slavePorts[pkt->getSrc()]->name(), pkt->getAddr(),
             pkt->cmdString());
 
-    // we should always see a request routed based on the address
-    assert(pkt->isRequest());
-
     // forward to all snoopers but the source
     std::pair<MemCmd, Tick> snoop_result = forwardAtomic(pkt, pkt->getSrc());
     MemCmd snoop_response_cmd = snoop_result.first;
@@ -565,9 +574,6 @@ Bus::recvAtomicSnoop(PacketPtr pkt)
             masterPorts[pkt->getSrc()]->name(), pkt->getAddr(),
             pkt->cmdString());
 
-    // we should always see a request routed based on the address
-    assert(pkt->isRequest());
-
     // forward to all snoopers
     std::pair<MemCmd, Tick> snoop_result =
         forwardAtomic(pkt, Port::INVALID_PORT_ID);
@@ -637,9 +643,6 @@ Bus::recvFunctional(PacketPtr pkt)
                 pkt->cmdString());
     }
 
-    // we should always see a request routed based on the address
-    assert(pkt->isRequest());
-
     // forward to all snoopers but the source
     forwardFunctional(pkt, pkt->getSrc());
 
@@ -663,9 +666,6 @@ Bus::recvFunctionalSnoop(PacketPtr pkt)
                 pkt->cmdString());
     }
 
-    // we should always see a request routed based on the address
-    assert(pkt->isRequest());
-
     // forward to all snoopers
     forwardFunctional(pkt, Port::INVALID_PORT_ID);
 }
diff --git a/src/mem/bus.hh b/src/mem/bus.hh
index bf64203bf..4ccb586e3 100644
--- a/src/mem/bus.hh
+++ b/src/mem/bus.hh
@@ -89,14 +89,14 @@ class Bus : public MemObject
         /**
          * When receiving a timing request, pass it to the bus.
          */
-        virtual bool recvTiming(PacketPtr pkt)
-        { pkt->setSrc(id); return bus->recvTiming(pkt); }
+        virtual bool recvTimingReq(PacketPtr pkt)
+        { pkt->setSrc(id); return bus->recvTimingReq(pkt); }
 
         /**
          * When receiving a timing snoop response, pass it to the bus.
          */
-        virtual bool recvTimingSnoop(PacketPtr pkt)
-        { pkt->setSrc(id); return bus->recvTimingSnoop(pkt); }
+        virtual bool recvTimingSnoopResp(PacketPtr pkt)
+        { pkt->setSrc(id); return bus->recvTimingSnoopResp(pkt); }
 
         /**
          * When receiving an atomic request, pass it to the bus.
@@ -163,14 +163,14 @@ class Bus : public MemObject
         /**
          * When receiving a timing response, pass it to the bus.
          */
-        virtual bool recvTiming(PacketPtr pkt)
-        { pkt->setSrc(id); return bus->recvTiming(pkt); }
+        virtual bool recvTimingResp(PacketPtr pkt)
+        { pkt->setSrc(id); return bus->recvTimingResp(pkt); }
 
         /**
          * When receiving a timing snoop request, pass it to the bus.
          */
-        virtual bool recvTimingSnoop(PacketPtr pkt)
-        { pkt->setSrc(id); return bus->recvTimingSnoop(pkt); }
+        virtual void recvTimingSnoopReq(PacketPtr pkt)
+        { pkt->setSrc(id); return bus->recvTimingSnoopReq(pkt); }
 
         /**
          * When receiving an atomic snoop request, pass it to the bus.
@@ -228,12 +228,20 @@ class Bus : public MemObject
     std::set<RequestPtr> outstandingReq;
 
     /** Function called by the port when the bus is recieving a Timing
-      transaction.*/
-    bool recvTiming(PacketPtr pkt);
+      request packet.*/
+    bool recvTimingReq(PacketPtr pkt);
+
+    /** Function called by the port when the bus is recieving a Timing
+      response packet.*/
+    bool recvTimingResp(PacketPtr pkt);
 
     /** Function called by the port when the bus is recieving a timing
-        snoop transaction.*/
-    bool recvTimingSnoop(PacketPtr pkt);
+        snoop request.*/
+    void recvTimingSnoopReq(PacketPtr pkt);
+
+    /** Function called by the port when the bus is recieving a timing
+        snoop response.*/
+    bool recvTimingSnoopResp(PacketPtr pkt);
 
     /**
      * Forward a timing packet to our snoopers, potentially excluding
diff --git a/src/mem/cache/base.hh b/src/mem/cache/base.hh
index b24e595b7..55d5e85e1 100644
--- a/src/mem/cache/base.hh
+++ b/src/mem/cache/base.hh
@@ -148,7 +148,7 @@ class BaseCache : public MemObject
       protected:
 
         CacheMasterPort(const std::string &_name, BaseCache *_cache,
-                        PacketQueue &_queue) :
+                        MasterPacketQueue &_queue) :
             QueuedMasterPort(_name, _cache, _queue)
         { }
 
@@ -196,7 +196,7 @@ class BaseCache : public MemObject
                        const std::string &_label);
 
         /** A normal packet queue used to store responses. */
-        PacketQueue queue;
+        SlavePacketQueue queue;
 
         bool blocked;
 
diff --git a/src/mem/cache/cache.hh b/src/mem/cache/cache.hh
index a774a356c..d2110adce 100644
--- a/src/mem/cache/cache.hh
+++ b/src/mem/cache/cache.hh
@@ -90,9 +90,9 @@ class Cache : public BaseCache
 
       protected:
 
-        virtual bool recvTimingSnoop(PacketPtr pkt);
+        virtual bool recvTimingSnoopResp(PacketPtr pkt);
 
-        virtual bool recvTiming(PacketPtr pkt);
+        virtual bool recvTimingReq(PacketPtr pkt);
 
         virtual Tick recvAtomic(PacketPtr pkt);
 
@@ -116,7 +116,7 @@ class Cache : public BaseCache
      * current MSHR status. This queue has a pointer to our specific
      * cache implementation and is used by the MemSidePort.
      */
-    class MemSidePacketQueue : public PacketQueue
+    class MemSidePacketQueue : public MasterPacketQueue
     {
 
       protected:
@@ -125,9 +125,9 @@ class Cache : public BaseCache
 
       public:
 
-        MemSidePacketQueue(Cache<TagStore> &cache, Port &port,
+        MemSidePacketQueue(Cache<TagStore> &cache, MasterPort &port,
                            const std::string &label) :
-            PacketQueue(cache, port, label), cache(cache) { }
+            MasterPacketQueue(cache, port, label), cache(cache) { }
 
         /**
          * Override the normal sendDeferredPacket and do not only
@@ -154,9 +154,9 @@ class Cache : public BaseCache
 
       protected:
 
-        virtual bool recvTimingSnoop(PacketPtr pkt);
+        virtual void recvTimingSnoopReq(PacketPtr pkt);
 
-        virtual bool recvTiming(PacketPtr pkt);
+        virtual bool recvTimingResp(PacketPtr pkt);
 
         virtual Tick recvAtomicSnoop(PacketPtr pkt);
 
diff --git a/src/mem/cache/cache_impl.hh b/src/mem/cache/cache_impl.hh
index fcdac1116..008bbb8d9 100644
--- a/src/mem/cache/cache_impl.hh
+++ b/src/mem/cache/cache_impl.hh
@@ -417,7 +417,7 @@ Cache<TagStore>::timingAccess(PacketPtr pkt)
             Packet *snoopPkt = new Packet(pkt, true);  // clear flags
             snoopPkt->setExpressSnoop();
             snoopPkt->assertMemInhibit();
-            memSidePort->sendTiming(snoopPkt);
+            memSidePort->sendTimingReq(snoopPkt);
             // main memory will delete snoopPkt
         }
         // since we're the official target but we aren't responding,
@@ -1181,7 +1181,7 @@ Cache<TagStore>::handleSnoop(PacketPtr pkt, BlkType *blk,
             Packet snoopPkt(pkt, true);  // clear flags
             snoopPkt.setExpressSnoop();
             snoopPkt.senderState = new ForwardResponseRecord(pkt, this);
-            cpuSidePort->sendTimingSnoop(&snoopPkt);
+            cpuSidePort->sendTimingSnoopReq(&snoopPkt);
             if (snoopPkt.memInhibitAsserted()) {
                 // cache-to-cache response from some upper cache
                 assert(!alreadyResponded);
@@ -1336,11 +1336,9 @@ Cache<TagStore>::snoopTiming(PacketPtr pkt)
 
 template<class TagStore>
 bool
-Cache<TagStore>::CpuSidePort::recvTimingSnoop(PacketPtr pkt)
+Cache<TagStore>::CpuSidePort::recvTimingSnoopResp(PacketPtr pkt)
 {
     // Express snoop responses from master to slave, e.g., from L1 to L2
-    assert(pkt->isResponse());
-
     cache->timingAccess(pkt);
     return true;
 }
@@ -1492,7 +1490,7 @@ Cache<TagStore>::getTimingPacket()
             PacketPtr snoop_pkt = new Packet(tgt_pkt, true);
             snoop_pkt->setExpressSnoop();
             snoop_pkt->senderState = mshr;
-            cpuSidePort->sendTimingSnoop(snoop_pkt);
+            cpuSidePort->sendTimingSnoopReq(snoop_pkt);
 
             if (snoop_pkt->memInhibitAsserted()) {
                 markInService(mshr, snoop_pkt);
@@ -1557,9 +1555,8 @@ Cache<TagStore>::CpuSidePort::getAddrRanges()
 
 template<class TagStore>
 bool
-Cache<TagStore>::CpuSidePort::recvTiming(PacketPtr pkt)
+Cache<TagStore>::CpuSidePort::recvTimingReq(PacketPtr pkt)
 {
-    assert(pkt->isRequest());
     // always let inhibited requests through even if blocked
     if (!pkt->memInhibitAsserted() && blocked) {
         DPRINTF(Cache,"Scheduling a retry while blocked\n");
@@ -1575,7 +1572,6 @@ template<class TagStore>
 Tick
 Cache<TagStore>::CpuSidePort::recvAtomic(PacketPtr pkt)
 {
-    assert(pkt->isRequest());
     // atomic request
     return cache->atomicAccess(pkt);
 }
@@ -1584,7 +1580,6 @@ template<class TagStore>
 void
 Cache<TagStore>::CpuSidePort::recvFunctional(PacketPtr pkt)
 {
-    assert(pkt->isRequest());
     // functional request
     cache->functionalAccess(pkt, true);
 }
@@ -1605,7 +1600,7 @@ CpuSidePort::CpuSidePort(const std::string &_name, Cache<TagStore> *_cache,
 
 template<class TagStore>
 bool
-Cache<TagStore>::MemSidePort::recvTiming(PacketPtr pkt)
+Cache<TagStore>::MemSidePort::recvTimingResp(PacketPtr pkt)
 {
     // this needs to be fixed so that the cache updates the mshr and sends the
     // packet back out on the link, but it probably won't happen so until this
@@ -1613,27 +1608,23 @@ Cache<TagStore>::MemSidePort::recvTiming(PacketPtr pkt)
     if (pkt->wasNacked())
         panic("Need to implement cache resending nacked packets!\n");
 
-    assert(pkt->isResponse());
     cache->handleResponse(pkt);
     return true;
 }
 
 // Express snooping requests to memside port
 template<class TagStore>
-bool
-Cache<TagStore>::MemSidePort::recvTimingSnoop(PacketPtr pkt)
+void
+Cache<TagStore>::MemSidePort::recvTimingSnoopReq(PacketPtr pkt)
 {
     // handle snooping requests
-    assert(pkt->isRequest());
     cache->snoopTiming(pkt);
-    return true;
 }
 
 template<class TagStore>
 Tick
 Cache<TagStore>::MemSidePort::recvAtomicSnoop(PacketPtr pkt)
 {
-    assert(pkt->isRequest());
     // atomic snoop
     return cache->snoopAtomic(pkt);
 }
@@ -1642,7 +1633,6 @@ template<class TagStore>
 void
 Cache<TagStore>::MemSidePort::recvFunctionalSnoop(PacketPtr pkt)
 {
-    assert(pkt->isRequest());
     // functional snoop (note that in contrast to atomic we don't have
     // a specific functionalSnoop method, as they have the same
     // behaviour regardless)
@@ -1668,7 +1658,7 @@ Cache<TagStore>::MemSidePacketQueue::sendDeferredPacket()
         } else {
             MSHR *mshr = dynamic_cast<MSHR*>(pkt->senderState);
 
-            waitingOnRetry = !port.sendTiming(pkt);
+            waitingOnRetry = !masterPort.sendTimingReq(pkt);
 
             if (waitingOnRetry) {
                 DPRINTF(CachePort, "now waiting on a retry\n");
diff --git a/src/mem/mport.hh b/src/mem/mport.hh
index 7f9e8f4e0..b74761256 100644
--- a/src/mem/mport.hh
+++ b/src/mem/mport.hh
@@ -82,12 +82,12 @@ class MessageMasterPort : public QueuedMasterPort
     virtual ~MessageMasterPort()
     {}
 
-    bool recvTiming(PacketPtr pkt) { recvResponse(pkt); return true; }
+    bool recvTimingResp(PacketPtr pkt) { recvResponse(pkt); return true; }
 
   protected:
 
     /** A packet queue for outgoing packets. */
-    PacketQueue queue;
+    MasterPacketQueue queue;
 
     // Accept and ignore responses.
     virtual Tick recvResponse(PacketPtr pkt)
diff --git a/src/mem/packet_queue.cc b/src/mem/packet_queue.cc
index bffae5674..ab50fd567 100644
--- a/src/mem/packet_queue.cc
+++ b/src/mem/packet_queue.cc
@@ -46,9 +46,8 @@
 
 using namespace std;
 
-PacketQueue::PacketQueue(EventManager& _em, Port& _port,
-                         const std::string _label)
-    : em(_em), label(_label), sendEvent(this), drainEvent(NULL), port(_port),
+PacketQueue::PacketQueue(EventManager& _em, const std::string& _label)
+    : em(_em), sendEvent(this), drainEvent(NULL), label(_label),
       waitingOnRetry(false)
 {
 }
@@ -142,11 +141,10 @@ void PacketQueue::trySendTiming()
     DeferredPacket dp = transmitList.front();
     transmitList.pop_front();
 
-    // attempt to send the packet and remember the outcome
-    if (!dp.sendAsSnoop)
-        waitingOnRetry = !port.sendTiming(dp.pkt);
-    else
-        waitingOnRetry = !port.sendTimingSnoop(dp.pkt);
+    // use the appropriate implementation of sendTiming based on the
+    // type of port associated with the queue, and whether the packet
+    // is to be sent as a snoop or not
+    waitingOnRetry = !sendTiming(dp.pkt, dp.sendAsSnoop);
 
     if (waitingOnRetry) {
         // put the packet back at the front of the list (packet should
@@ -206,3 +204,33 @@ PacketQueue::drain(Event *de)
     drainEvent = de;
     return 1;
 }
+
+MasterPacketQueue::MasterPacketQueue(EventManager& _em, MasterPort& _masterPort,
+                                     const std::string _label)
+    : PacketQueue(_em, _label), masterPort(_masterPort)
+{
+}
+
+bool
+MasterPacketQueue::sendTiming(PacketPtr pkt, bool send_as_snoop)
+{
+    // attempt to send the packet and return according to the outcome
+    if (!send_as_snoop)
+        return masterPort.sendTimingReq(pkt);
+    else
+        return masterPort.sendTimingSnoopResp(pkt);
+}
+
+SlavePacketQueue::SlavePacketQueue(EventManager& _em, SlavePort& _slavePort,
+                                   const std::string _label)
+    : PacketQueue(_em, _label), slavePort(_slavePort)
+{
+}
+
+bool
+SlavePacketQueue::sendTiming(PacketPtr pkt, bool send_as_snoop)
+{
+    // we should never have queued snoop requests
+    assert(!send_as_snoop);
+    return slavePort.sendTimingResp(pkt);
+}
diff --git a/src/mem/packet_queue.hh b/src/mem/packet_queue.hh
index fbcd7d449..0171eb9a3 100644
--- a/src/mem/packet_queue.hh
+++ b/src/mem/packet_queue.hh
@@ -86,9 +86,6 @@ class PacketQueue
     /** The manager which is used for the event queue */
     EventManager& em;
 
-    /** Label to use for print request packets label stack. */
-    const std::string label;
-
     /** This function attempts to send deferred packets.  Scheduled to
      * be called in the future via SendEvent. */
     void processSendEvent();
@@ -104,8 +101,8 @@ class PacketQueue
 
   protected:
 
-    /** The port used to send the packets. */
-    Port& port;
+    /** Label to use for print request packets label stack. */
+    const std::string label;
 
     /** Remember whether we're awaiting a retry from the bus. */
     bool waitingOnRetry;
@@ -135,6 +132,11 @@ class PacketQueue
     void trySendTiming();
 
     /**
+     *
+     */
+    virtual bool sendTiming(PacketPtr pkt, bool send_as_snoop) = 0;
+
+    /**
      * Based on the transmit list, or the provided time, schedule a
      * send event if there are packets to send. If we are idle and
      * asked to drain then do so.
@@ -152,31 +154,28 @@ class PacketQueue
      */
     virtual void recvRangeChange() { }
 
-  public:
-
     /**
-     * Create a packet queue, linked to an event manager, a port used
-     * to send the packets, and potentially give it a label that will
-     * be used for functional print request packets.
+     * Create a packet queue, linked to an event manager, and a label
+     * that will be used for functional print request packets.
      *
      * @param _em Event manager used for scheduling this queue
-     * @param _port Port used to send the packets
      * @param _label Label to push on the label stack for print request packets
      */
-    PacketQueue(EventManager& _em, Port& _port,
-                const std::string _label = "PacketQueue");
+    PacketQueue(EventManager& _em, const std::string& _label);
 
     /**
      * Virtual desctructor since the class may be used as a base class.
      */
     virtual ~PacketQueue();
 
+  public:
+
     /**
-     * Provide a name to simplify debugging. Base it on the port.
+     * Provide a name to simplify debugging.
      *
      * @return A complete name, appended to module and port
      */
-    const std::string name() const { return port.name() + "-queue"; }
+    virtual const std::string name() const = 0;
 
     /** Check the list of buffered packets against the supplied
      * functional request. */
@@ -217,4 +216,63 @@ class PacketQueue
     unsigned int drain(Event *de);
 };
 
+class MasterPacketQueue : public PacketQueue
+{
+
+  protected:
+
+    MasterPort& masterPort;
+
+  public:
+
+    /**
+     * Create a master packet queue, linked to an event manager, a
+     * master port, and a label that will be used for functional print
+     * request packets.
+     *
+     * @param _em Event manager used for scheduling this queue
+     * @param _masterPort Master port used to send the packets
+     * @param _label Label to push on the label stack for print request packets
+     */
+    MasterPacketQueue(EventManager& _em, MasterPort& _masterPort,
+                      const std::string _label = "MasterPacketQueue");
+
+    virtual ~MasterPacketQueue() { }
+
+    const std::string name() const
+    { return masterPort.name() + "-" + label; }
+
+    bool sendTiming(PacketPtr pkt, bool send_as_snoop);
+};
+
+class SlavePacketQueue : public PacketQueue
+{
+
+  protected:
+
+    SlavePort& slavePort;
+
+  public:
+
+    /**
+     * Create a slave packet queue, linked to an event manager, a
+     * slave port, and a label that will be used for functional print
+     * request packets.
+     *
+     * @param _em Event manager used for scheduling this queue
+     * @param _slavePort Slave port used to send the packets
+     * @param _label Label to push on the label stack for print request packets
+     */
+    SlavePacketQueue(EventManager& _em, SlavePort& _slavePort,
+                     const std::string _label = "SlavePacketQueue");
+
+    virtual ~SlavePacketQueue() { }
+
+    const std::string name() const
+    { return slavePort.name() + "-" + label; }
+
+    bool sendTiming(PacketPtr pkt, bool send_as_snoop);
+
+};
+
 #endif // __MEM_PACKET_QUEUE_HH__
diff --git a/src/mem/port.cc b/src/mem/port.cc
index fc3a42c02..9cebd5897 100644
--- a/src/mem/port.cc
+++ b/src/mem/port.cc
@@ -107,15 +107,31 @@ MasterPort::peerBlockSize() const
 Tick
 MasterPort::sendAtomic(PacketPtr pkt)
 {
+    assert(pkt->isRequest());
     return _slavePort->recvAtomic(pkt);
 }
 
 void
 MasterPort::sendFunctional(PacketPtr pkt)
 {
+    assert(pkt->isRequest());
     return _slavePort->recvFunctional(pkt);
 }
 
+bool
+MasterPort::sendTimingReq(PacketPtr pkt)
+{
+    assert(pkt->isRequest());
+    return _slavePort->recvTimingReq(pkt);
+}
+
+bool
+MasterPort::sendTimingSnoopResp(PacketPtr pkt)
+{
+    assert(pkt->isResponse());
+    return _slavePort->recvTimingSnoopResp(pkt);
+}
+
 void
 MasterPort::printAddr(Addr a)
 {
@@ -171,11 +187,27 @@ SlavePort::isConnected() const
 Tick
 SlavePort::sendAtomicSnoop(PacketPtr pkt)
 {
+    assert(pkt->isRequest());
     return _masterPort->recvAtomicSnoop(pkt);
 }
 
 void
 SlavePort::sendFunctionalSnoop(PacketPtr pkt)
 {
+    assert(pkt->isRequest());
     return _masterPort->recvFunctionalSnoop(pkt);
 }
+
+bool
+SlavePort::sendTimingResp(PacketPtr pkt)
+{
+    assert(pkt->isResponse());
+    return _masterPort->recvTimingResp(pkt);
+}
+
+void
+SlavePort::sendTimingSnoopReq(PacketPtr pkt)
+{
+    assert(pkt->isRequest());
+    _masterPort->recvTimingSnoopReq(pkt);
+}
diff --git a/src/mem/port.hh b/src/mem/port.hh
index e1f643e8e..840952354 100644
--- a/src/mem/port.hh
+++ b/src/mem/port.hh
@@ -73,8 +73,7 @@ class MemObject;
  * opposite role.
  *
  * Each port has a name and an owner, and enables three basic types of
- * accesses to the peer port: sendFunctional, sendAtomic and
- * sendTiming.
+ * accesses to the peer port: functional, atomic and timing.
  */
 class Port
 {
@@ -130,61 +129,18 @@ class Port
 
   protected:
 
-    /** These functions are protected because they should only be
-     * called by a peer port, never directly by any outside object. */
-
-    /**
-     * Receive a timing request or response packet from the peer port.
-     */
-    virtual bool recvTiming(PacketPtr pkt) = 0;
-
-    /**
-     * Receive a timing snoop request or snoop response packet from
-     * the peer port.
-     */
-    virtual bool recvTimingSnoop(PacketPtr pkt)
-    {
-        panic("%s was not expecting a timing snoop\n", name());
-        return false;
-    }
-
     /**
-     * Called by a peer port if sendTiming or sendTimingSnoop was
-     * unsuccesful, and had to wait.
+     * Called by a peer port if sendTimingReq, sendTimingResp or
+     * sendTimingSnoopResp was unsuccesful, and had to wait.
      */
     virtual void recvRetry() = 0;
 
   public:
 
     /**
-     * Attempt to send a timing request or response packet to the peer
-     * port by calling its receive function. If the send does not
-     * succeed, as indicated by the return value, then the sender must
-     * wait for a recvRetry at which point it can re-issue a
-     * sendTiming.
-     *
-     * @param pkt Packet to send.
-     *
-     * @return If the send was succesful or not.
-    */
-    bool sendTiming(PacketPtr pkt) { return peer->recvTiming(pkt); }
-
-    /**
-     * Attempt to send a timing snoop request or snoop response packet
-     * to the peer port by calling its receive function. If the send
-     * does not succeed, as indicated by the return value, then the
-     * sender must wait for a recvRetry at which point it can re-issue
-     * a sendTimingSnoop.
-     *
-     * @param pkt Packet to send.
-     *
-     * @return If the send was succesful or not.
-    */
-    bool sendTimingSnoop(PacketPtr pkt) { return peer->recvTimingSnoop(pkt); }
-
-    /**
      * Send a retry to a peer port that previously attempted a
-     * sendTiming or sendTimingSnoop which was unsuccessful.
+     * sendTimingReq, sendTimingResp or sendTimingSnoopResp which was
+     * unsuccessful.
      */
     void sendRetry() { return peer->recvRetry(); }
 
@@ -202,6 +158,8 @@ class SlavePort;
 class MasterPort : public Port
 {
 
+    friend class SlavePort;
+
   private:
 
     SlavePort* _slavePort;
@@ -237,30 +195,28 @@ class MasterPort : public Port
     void sendFunctional(PacketPtr pkt);
 
     /**
-     * Receive an atomic snoop request packet from the slave port.
-     */
-    virtual Tick recvAtomicSnoop(PacketPtr pkt)
-    {
-        panic("%s was not expecting an atomic snoop\n", name());
-        return 0;
-    }
-
-    /**
-     * Receive a functional snoop request packet from the slave port.
-     */
-    virtual void recvFunctionalSnoop(PacketPtr pkt)
-    {
-        panic("%s was not expecting a functional snoop\n", name());
-    }
+     * Attempt to send a timing request to the slave port by calling
+     * its corresponding receive function. If the send does not
+     * succeed, as indicated by the return value, then the sender must
+     * wait for a recvRetry at which point it can re-issue a
+     * sendTimingReq.
+     *
+     * @param pkt Packet to send.
+     *
+     * @return If the send was succesful or not.
+    */
+    bool sendTimingReq(PacketPtr pkt);
 
     /**
-     * Called to receive an address range change from the peer slave
-     * port. the default implementation ignored the change and does
-     * nothing. Override this function in a derived class if the owner
-     * needs to be aware of he laesddress ranges, e.g. in an
-     * interconnect component like a bus.
+     * Attempt to send a timing snoop response packet to the slave
+     * port by calling its corresponding receive function. If the send
+     * does not succeed, as indicated by the return value, then the
+     * sender must wait for a recvRetry at which point it can re-issue
+     * a sendTimingSnoopResp.
+     *
+     * @param pkt Packet to send.
      */
-    virtual void recvRangeChange() { }
+    bool sendTimingSnoopResp(PacketPtr pkt);
 
     /**
      * Determine if this master port is snooping or not. The default
@@ -288,6 +244,47 @@ class MasterPort : public Port
      * that address throughout the memory system.  For debugging.
      */
     void printAddr(Addr a);
+
+  protected:
+
+    /**
+     * Receive an atomic snoop request packet from the slave port.
+     */
+    virtual Tick recvAtomicSnoop(PacketPtr pkt)
+    {
+        panic("%s was not expecting an atomic snoop request\n", name());
+        return 0;
+    }
+
+    /**
+     * Receive a functional snoop request packet from the slave port.
+     */
+    virtual void recvFunctionalSnoop(PacketPtr pkt)
+    {
+        panic("%s was not expecting a functional snoop request\n", name());
+    }
+
+    /**
+     * Receive a timing response from the slave port.
+     */
+    virtual bool recvTimingResp(PacketPtr pkt) = 0;
+
+    /**
+     * Receive a timing snoop request from the slave port.
+     */
+    virtual void recvTimingSnoopReq(PacketPtr pkt)
+    {
+        panic("%s was not expecting a timing snoop request\n", name());
+    }
+
+    /**
+     * Called to receive an address range change from the peer slave
+     * port. the default implementation ignored the change and does
+     * nothing. Override this function in a derived class if the owner
+     * needs to be aware of he laesddress ranges, e.g. in an
+     * interconnect component like a bus.
+     */
+    virtual void recvRangeChange() { }
 };
 
 /**
@@ -299,6 +296,8 @@ class MasterPort : public Port
 class SlavePort : public Port
 {
 
+    friend class MasterPort;
+
   private:
 
     MasterPort* _masterPort;
@@ -334,14 +333,26 @@ class SlavePort : public Port
     void sendFunctionalSnoop(PacketPtr pkt);
 
     /**
-     * Receive an atomic request packet from the master port.
-     */
-    virtual Tick recvAtomic(PacketPtr pkt) = 0;
+     * Attempt to send a timing response to the master port by calling
+     * its corresponding receive function. If the send does not
+     * succeed, as indicated by the return value, then the sender must
+     * wait for a recvRetry at which point it can re-issue a
+     * sendTimingResp.
+     *
+     * @param pkt Packet to send.
+     *
+     * @return If the send was succesful or not.
+    */
+    bool sendTimingResp(PacketPtr pkt);
 
     /**
-     * Receive a functional request packet from the master port.
+     * Attempt to send a timing snoop request packet to the master port
+     * by calling its corresponding receive function. Snoop requests
+     * always succeed and hence no return value is needed.
+     *
+     * @param pkt Packet to send.
      */
-    virtual void recvFunctional(PacketPtr pkt) = 0;
+    void sendTimingSnoopReq(PacketPtr pkt);
 
     /**
      * Called by a peer port in order to determine the block size of
@@ -367,6 +378,32 @@ class SlavePort : public Port
      * @return a list of ranges responded to
      */
     virtual AddrRangeList getAddrRanges() = 0;
+
+  protected:
+
+    /**
+     * Receive an atomic request packet from the master port.
+     */
+    virtual Tick recvAtomic(PacketPtr pkt) = 0;
+
+    /**
+     * Receive a functional request packet from the master port.
+     */
+    virtual void recvFunctional(PacketPtr pkt) = 0;
+
+    /**
+     * Receive a timing request from the master port.
+     */
+    virtual bool recvTimingReq(PacketPtr pkt) = 0;
+
+    /**
+     * Receive a timing snoop response from the master port.
+     */
+    virtual bool recvTimingSnoopResp(PacketPtr pkt)
+    {
+        panic("%s was not expecting a timing snoop response\n", name());
+    }
+
 };
 
 #endif //__MEM_PORT_HH__
diff --git a/src/mem/qport.hh b/src/mem/qport.hh
index 6ee71a572..1d0544dfa 100644
--- a/src/mem/qport.hh
+++ b/src/mem/qport.hh
@@ -62,7 +62,7 @@ class QueuedSlavePort : public SlavePort
   protected:
 
     /** Packet queue used to store outgoing requests and responses. */
-    PacketQueue &queue;
+    SlavePacketQueue &queue;
 
      /** This function is notification that the device should attempt to send a
       * packet again. */
@@ -78,7 +78,7 @@ class QueuedSlavePort : public SlavePort
      * QueuePort constructor.
      */
     QueuedSlavePort(const std::string& name, MemObject* owner,
-                    PacketQueue &queue) :
+                    SlavePacketQueue &queue) :
         SlavePort(name, owner), queue(queue)
     { }
 
@@ -103,7 +103,7 @@ class QueuedMasterPort : public MasterPort
   protected:
 
     /** Packet queue used to store outgoing requests and responses. */
-    PacketQueue &queue;
+    MasterPacketQueue &queue;
 
      /** This function is notification that the device should attempt to send a
       * packet again. */
@@ -119,7 +119,7 @@ class QueuedMasterPort : public MasterPort
      * QueuePort constructor.
      */
     QueuedMasterPort(const std::string& name, MemObject* owner,
-                    PacketQueue &queue) :
+                     MasterPacketQueue &queue) :
         MasterPort(name, owner), queue(queue)
     { }
 
diff --git a/src/mem/ruby/system/RubyPort.cc b/src/mem/ruby/system/RubyPort.cc
index ef9f59645..53b6e8e6d 100644
--- a/src/mem/ruby/system/RubyPort.cc
+++ b/src/mem/ruby/system/RubyPort.cc
@@ -141,14 +141,12 @@ RubyPort::M5Port::recvAtomic(PacketPtr pkt)
 
 
 bool
-RubyPort::PioPort::recvTiming(PacketPtr pkt)
+RubyPort::PioPort::recvTimingResp(PacketPtr pkt)
 {
     // In FS mode, ruby memory will receive pio responses from devices
     // and it must forward these responses back to the particular CPU.
     DPRINTF(RubyPort,  "Pio response for address %#x\n", pkt->getAddr());
 
-    assert(pkt->isResponse());
-
     // First we must retrieve the request port from the sender State
     RubyPort::SenderState *senderState =
       safe_cast<RubyPort::SenderState *>(pkt->senderState);
@@ -159,24 +157,23 @@ RubyPort::PioPort::recvTiming(PacketPtr pkt)
     pkt->senderState = senderState->saved;
     delete senderState;
 
-    port->sendTiming(pkt);
+    port->sendTimingResp(pkt);
 
     return true;
 }
 
 bool
-RubyPort::M5Port::recvTiming(PacketPtr pkt)
+RubyPort::M5Port::recvTimingReq(PacketPtr pkt)
 {
     DPRINTF(RubyPort,
             "Timing access caught for address %#x\n", pkt->getAddr());
 
-    //dsm: based on SimpleTimingPort::recvTiming(pkt);
+    //dsm: based on SimpleTimingPort::recvTimingReq(pkt);
 
     // The received packets should only be M5 requests, which should never
     // get nacked.  There used to be code to hanldle nacks here, but
     // I'm pretty sure it didn't work correctly with the drain code,
     // so that would need to be fixed if we ever added it back.
-    assert(pkt->isRequest());
 
     if (pkt->memInhibitAsserted()) {
         warn("memInhibitAsserted???");
diff --git a/src/mem/ruby/system/RubyPort.hh b/src/mem/ruby/system/RubyPort.hh
index f41c98f55..8833efb6e 100644
--- a/src/mem/ruby/system/RubyPort.hh
+++ b/src/mem/ruby/system/RubyPort.hh
@@ -62,7 +62,7 @@ class RubyPort : public MemObject
     {
       private:
 
-        PacketQueue queue;
+        SlavePacketQueue queue;
         RubyPort *ruby_port;
         RubySystem* ruby_system;
         bool _onRetryList;
@@ -83,7 +83,7 @@ class RubyPort : public MemObject
         { _onRetryList = newVal; }
 
       protected:
-        virtual bool recvTiming(PacketPtr pkt);
+        virtual bool recvTimingReq(PacketPtr pkt);
         virtual Tick recvAtomic(PacketPtr pkt);
         virtual void recvFunctional(PacketPtr pkt);
         virtual AddrRangeList getAddrRanges();
@@ -100,7 +100,7 @@ class RubyPort : public MemObject
     {
       private:
 
-        PacketQueue queue;
+        MasterPacketQueue queue;
 
         RubyPort *ruby_port;
 
@@ -109,7 +109,7 @@ class RubyPort : public MemObject
         bool sendNextCycle(PacketPtr pkt);
 
       protected:
-        virtual bool recvTiming(PacketPtr pkt);
+        virtual bool recvTimingResp(PacketPtr pkt);
     };
 
     friend class PioPort;
diff --git a/src/mem/tport.cc b/src/mem/tport.cc
index db2c72bbc..c071ef18c 100644
--- a/src/mem/tport.cc
+++ b/src/mem/tport.cc
@@ -53,7 +53,6 @@ SimpleTimingPort::SimpleTimingPort(const std::string& _name,
 void
 SimpleTimingPort::recvFunctional(PacketPtr pkt)
 {
-    assert(pkt->isRequest());
     if (!queue.checkFunctional(pkt)) {
         // do an atomic access and throw away the returned latency
         recvAtomic(pkt);
@@ -61,11 +60,8 @@ SimpleTimingPort::recvFunctional(PacketPtr pkt)
 }
 
 bool
-SimpleTimingPort::recvTiming(PacketPtr pkt)
+SimpleTimingPort::recvTimingReq(PacketPtr pkt)
 {
-    // the port is a slave and should hence only get timing requests
-    assert(pkt->isRequest());
-
     if (pkt->memInhibitAsserted()) {
         // snooper will supply based on copy of packet
         // still target's responsibility to delete packet
diff --git a/src/mem/tport.hh b/src/mem/tport.hh
index 91706fbe9..db5a074fb 100644
--- a/src/mem/tport.hh
+++ b/src/mem/tport.hh
@@ -54,7 +54,7 @@
 
 /**
  * The simple timing port uses a queued port to implement
- * recvFunctional and recvTiming through recvAtomic. It is always a
+ * recvFunctional and recvTimingReq through recvAtomic. It is always a
  * slave port.
  */
 class SimpleTimingPort : public QueuedSlavePort
@@ -63,13 +63,13 @@ class SimpleTimingPort : public QueuedSlavePort
   protected:
 
     /** The packet queue used to store outgoing responses. */
-    PacketQueue queue;
+    SlavePacketQueue queue;
 
     /** Implemented using recvAtomic(). */
     void recvFunctional(PacketPtr pkt);
 
     /** Implemented using recvAtomic(). */
-    bool recvTiming(PacketPtr pkt);
+    bool recvTimingReq(PacketPtr pkt);
 
     virtual Tick recvAtomic(PacketPtr pkt) = 0;
 
@@ -77,7 +77,7 @@ class SimpleTimingPort : public QueuedSlavePort
 
     /**
      * Create a new SimpleTimingPort that relies on a packet queue to
-     * hold responses, and implements recvTiming and recvFunctional
+     * hold responses, and implements recvTimingReq and recvFunctional
      * through calls to recvAtomic. Once a request arrives, it is
      * passed to recvAtomic, and in the case of a timing access any
      * response is scheduled to be sent after the delay of the atomic
diff --git a/src/sim/system.hh b/src/sim/system.hh
index f7831d09c..6dc8d73e0 100644
--- a/src/sim/system.hh
+++ b/src/sim/system.hh
@@ -88,7 +88,7 @@ class System : public MemObject
         SystemPort(const std::string &_name, MemObject *_owner)
             : MasterPort(_name, _owner)
         { }
-        bool recvTiming(PacketPtr pkt)
+        bool recvTimingResp(PacketPtr pkt)
         { panic("SystemPort does not receive timing!\n"); return false; }
         void recvRetry()
         { panic("SystemPort does not expect retry!\n"); }