Mem: Use cycles to express cache-related latencies

This patch changes the cache-related latencies from an absolute time
expressed in Ticks, to a number of cycles that can be scaled with the
clock period of the caches. Ultimately this patch serves to enable
future work that involves dynamic frequency scaling. As an immediate
benefit it also makes it more convenient to specify cache performance
without implicitly assuming a specific CPU core operating frequency.

The stat blocked_cycles that actually counter in ticks is now updated
to count in cycles.

As the timing is now rounded to the clock edges of the cache, there
are some regressions that change. Plenty of them have very minor
changes, whereas some regressions with a short run-time are perturbed
quite significantly. A follow-on patch updates all the statistics for
the regressions.

20 files changed, 121 insertions, 67 deletions

diff --git a/src/mem/cache/BaseCache.py b/src/mem/cache/BaseCache.py
index fde0aa492..6fe73a9c2 100644
--- a/src/mem/cache/BaseCache.py
+++ b/src/mem/cache/BaseCache.py
@@ -1,3 +1,15 @@
+# Copyright (c) 2012 ARM Limited
+# All rights reserved.
+#
+# The license below extends only to copyright in the software and shall
+# not be construed as granting a license to any other intellectual
+# property including but not limited to intellectual property relating
+# to a hardware implementation of the functionality of the software
+# licensed hereunder.  You may use the software subject to the license
+# terms below provided that you ensure that this notice is replicated
+# unmodified and in its entirety in all distributions of the software,
+# modified or unmodified, in source code or in binary form.
+#
 # Copyright (c) 2005-2007 The Regents of The University of Michigan
 # All rights reserved.
 #
@@ -36,8 +48,8 @@ class BaseCache(MemObject):
     type = 'BaseCache'
     assoc = Param.Int("associativity")
     block_size = Param.Int("block size in bytes")
-    hit_latency = Param.Latency("The hit latency for this cache")
-    response_latency = Param.Latency(
+    hit_latency = Param.Cycles("The hit latency for this cache")
+    response_latency = Param.Cycles(
             "Additional cache latency for the return path to core on a miss");
     hash_delay = Param.Cycles(1, "time in cycles of hash access")
     max_miss_count = Param.Counter(0,
diff --git a/src/mem/cache/base.cc b/src/mem/cache/base.cc
index 4dd428a2e..c95999f3e 100644
--- a/src/mem/cache/base.cc
+++ b/src/mem/cache/base.cc
@@ -81,6 +81,10 @@ BaseCache::BaseCache(const Params *p)
       addrRanges(p->addr_ranges.begin(), p->addr_ranges.end()),
       system(p->system)
 {
+    // ensure the clock is not running at an unreasonable clock speed
+    if (clock == 1)
+        panic("Cache %s has a cycle time of 1 tick. Specify a clock.\n",
+              name());
 }
 
 void
diff --git a/src/mem/cache/base.hh b/src/mem/cache/base.hh
index da72667b3..2e31836c0 100644
--- a/src/mem/cache/base.hh
+++ b/src/mem/cache/base.hh
@@ -229,7 +229,7 @@ class BaseCache : public MemObject
     /**
      * The latency of a hit in this device.
      */
-    const Tick hitLatency;
+    const Cycles hitLatency;
 
     /**
      * The latency of sending reponse to its upper level cache/core on a
@@ -237,7 +237,7 @@ class BaseCache : public MemObject
      * miss is much quicker that the hit latency. The responseLatency parameter
      * tries to capture this latency.
      */
-    const Tick responseLatency;
+    const Cycles responseLatency;
 
     /** The number of targets for each MSHR. */
     const int numTarget;
@@ -260,7 +260,7 @@ class BaseCache : public MemObject
     uint64_t order;
 
     /** Stores time the cache blocked for statistics. */
-    Tick blockedCycle;
+    Cycles blockedCycle;
 
     /** Pointer to the MSHR that has no targets. */
     MSHR *noTargetMSHR;
@@ -492,7 +492,7 @@ class BaseCache : public MemObject
         uint8_t flag = 1 << cause;
         if (blocked == 0) {
             blocked_causes[cause]++;
-            blockedCycle = curTick();
+            blockedCycle = curCycle();
             cpuSidePort->setBlocked();
         }
         blocked |= flag;
@@ -512,7 +512,7 @@ class BaseCache : public MemObject
         blocked &= ~flag;
         DPRINTF(Cache,"Unblocking for cause %d, mask=%d\n", cause, blocked);
         if (blocked == 0) {
-            blocked_cycles[cause] += curTick() - blockedCycle;
+            blocked_cycles[cause] += curCycle() - blockedCycle;
             cpuSidePort->clearBlocked();
         }
     }
diff --git a/src/mem/cache/cache.hh b/src/mem/cache/cache.hh
index 3c34c10f7..be81736aa 100644
--- a/src/mem/cache/cache.hh
+++ b/src/mem/cache/cache.hh
@@ -206,7 +206,7 @@ class Cache : public BaseCache
      * @return Boolean indicating whether the request was satisfied.
      */
     bool access(PacketPtr pkt, BlkType *&blk,
-                int &lat, PacketList &writebacks);
+                Cycles &lat, PacketList &writebacks);
 
     /**
      *Handle doing the Compare and Swap function for SPARC.
@@ -272,7 +272,7 @@ class Cache : public BaseCache
     /**
      * Performs the access specified by the request.
      * @param pkt The request to perform.
-     * @return The result of the access.
+     * @return The number of ticks required for the access.
      */
     Tick atomicAccess(PacketPtr pkt);
 
@@ -299,9 +299,9 @@ class Cache : public BaseCache
      * Snoop for the provided request in the cache and return the estimated
      * time of completion.
      * @param pkt The memory request to snoop
-     * @return The estimated completion time.
+     * @return The number of cycles required for the snoop.
      */
-    Tick snoopAtomic(PacketPtr pkt);
+    Cycles snoopAtomic(PacketPtr pkt);
 
     /**
      * Squash all requests associated with specified thread.
diff --git a/src/mem/cache/cache_impl.hh b/src/mem/cache/cache_impl.hh
index a22003c4f..44acaef5b 100644
--- a/src/mem/cache/cache_impl.hh
+++ b/src/mem/cache/cache_impl.hh
@@ -275,7 +275,7 @@ Cache<TagStore>::squash(int threadNum)
 template<class TagStore>
 bool
 Cache<TagStore>::access(PacketPtr pkt, BlkType *&blk,
-                        int &lat, PacketList &writebacks)
+                        Cycles &lat, PacketList &writebacks)
 {
     if (pkt->req->isUncacheable()) {
         if (pkt->req->isClearLL()) {
@@ -392,7 +392,7 @@ Cache<TagStore>::timingAccess(PacketPtr pkt)
     pendingDelete.clear();
 
     // we charge hitLatency for doing just about anything here
-    Tick time =  curTick() + hitLatency;
+    Tick time = clockEdge(hitLatency);
 
     if (pkt->isResponse()) {
         // must be cache-to-cache response from upper to lower level
@@ -463,7 +463,7 @@ Cache<TagStore>::timingAccess(PacketPtr pkt)
         return true;
     }
 
-    int lat = hitLatency;
+    Cycles lat = hitLatency;
     BlkType *blk = NULL;
     PacketList writebacks;
 
@@ -505,7 +505,7 @@ Cache<TagStore>::timingAccess(PacketPtr pkt)
 
         if (needsResponse) {
             pkt->makeTimingResponse();
-            cpuSidePort->schedTimingResp(pkt, curTick()+lat);
+            cpuSidePort->schedTimingResp(pkt, clockEdge(lat));
         } else {
             /// @todo nominally we should just delete the packet here,
             /// however, until 4-phase stuff we can't because sending
@@ -637,7 +637,7 @@ template<class TagStore>
 Tick
 Cache<TagStore>::atomicAccess(PacketPtr pkt)
 {
-    int lat = hitLatency;
+    Cycles lat = hitLatency;
 
     // @TODO: make this a parameter
     bool last_level_cache = false;
@@ -657,7 +657,7 @@ Cache<TagStore>::atomicAccess(PacketPtr pkt)
             if (!last_level_cache) {
                 DPRINTF(Cache, "forwarding mem-inhibited %s on 0x%x\n",
                         pkt->cmdString(), pkt->getAddr());
-                lat += memSidePort->sendAtomic(pkt);
+                lat += ticksToCycles(memSidePort->sendAtomic(pkt));
             }
         } else {
             DPRINTF(Cache, "rcvd mem-inhibited %s on 0x%x: not responding\n",
@@ -693,7 +693,7 @@ Cache<TagStore>::atomicAccess(PacketPtr pkt)
         CacheBlk::State old_state = blk ? blk->status : 0;
 #endif
 
-        lat += memSidePort->sendAtomic(bus_pkt);
+        lat += ticksToCycles(memSidePort->sendAtomic(bus_pkt));
 
         DPRINTF(Cache, "Receive response: %s for addr %x in state %i\n",
                 bus_pkt->cmdString(), bus_pkt->getAddr(), old_state);
@@ -821,7 +821,7 @@ template<class TagStore>
 void
 Cache<TagStore>::handleResponse(PacketPtr pkt)
 {
-    Tick time = curTick() + hitLatency;
+    Tick time = clockEdge(hitLatency);
     MSHR *mshr = dynamic_cast<MSHR*>(pkt->senderState);
     bool is_error = pkt->isError();
 
@@ -901,7 +901,7 @@ Cache<TagStore>::handleResponse(PacketPtr pkt)
                 // responseLatency is the latency of the return path
                 // from lower level caches/memory to an upper level cache or
                 // the core.
-                completion_time = responseLatency +
+                completion_time = responseLatency * clock +
                     (transfer_offset ? pkt->finishTime : pkt->firstWordTime);
 
                 assert(!target->pkt->req->isUncacheable());
@@ -917,13 +917,13 @@ Cache<TagStore>::handleResponse(PacketPtr pkt)
                 // responseLatency is the latency of the return path
                 // from lower level caches/memory to an upper level cache or
                 // the core.
-                completion_time = responseLatency + pkt->finishTime;
+                completion_time = responseLatency * clock + pkt->finishTime;
                 target->pkt->req->setExtraData(0);
             } else {
                 // not a cache fill, just forwarding response
                 // responseLatency is the latency of the return path
                 // from lower level cahces/memory to the core.
-                completion_time = responseLatency + pkt->finishTime;
+                completion_time = responseLatency * clock + pkt->finishTime;
                 if (pkt->isRead() && !is_error) {
                     target->pkt->setData(pkt->getPtr<uint8_t>());
                 }
@@ -1173,7 +1173,7 @@ doTimingSupplyResponse(PacketPtr req_pkt, uint8_t *blk_data,
         // invalidate it.
         pkt->cmd = MemCmd::ReadRespWithInvalidate;
     }
-    memSidePort->schedTimingSnoopResp(pkt, curTick() + hitLatency);
+    memSidePort->schedTimingSnoopResp(pkt, clockEdge(hitLatency));
 }
 
 template<class TagStore>
@@ -1366,7 +1366,7 @@ Cache<TagStore>::CpuSidePort::recvTimingSnoopResp(PacketPtr pkt)
 }
 
 template<class TagStore>
-Tick
+Cycles
 Cache<TagStore>::snoopAtomic(PacketPtr pkt)
 {
     if (pkt->req->isUncacheable() || pkt->cmd == MemCmd::Writeback) {
diff --git a/src/mem/cache/prefetch/Prefetcher.py b/src/mem/cache/prefetch/Prefetcher.py
index fa926e235..e590410ae 100644
--- a/src/mem/cache/prefetch/Prefetcher.py
+++ b/src/mem/cache/prefetch/Prefetcher.py
@@ -1,8 +1,48 @@
-from m5.SimObject import SimObject
+# Copyright (c) 2012 ARM Limited
+# All rights reserved.
+#
+# The license below extends only to copyright in the software and shall
+# not be construed as granting a license to any other intellectual
+# property including but not limited to intellectual property relating
+# to a hardware implementation of the functionality of the software
+# licensed hereunder.  You may use the software subject to the license
+# terms below provided that you ensure that this notice is replicated
+# unmodified and in its entirety in all distributions of the software,
+# modified or unmodified, in source code or in binary form.
+#
+# Copyright (c) 2005 The Regents of The University of Michigan
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met: redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer;
+# redistributions in binary form must reproduce the above copyright
+# notice, this list of conditions and the following disclaimer in the
+# documentation and/or other materials provided with the distribution;
+# neither the name of the copyright holders nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#
+# Authors: Ron Dreslinski
+
+from ClockedObject import ClockedObject
 from m5.params import *
 from m5.proxy import *
 
-class BasePrefetcher(SimObject):
+class BasePrefetcher(ClockedObject):
     type = 'BasePrefetcher'
     abstract = True
     size = Param.Int(100,
@@ -13,8 +53,7 @@ class BasePrefetcher(SimObject):
          "Squash prefetches with a later time on a subsequent miss")
     degree = Param.Int(1,
          "Degree of the prefetch depth")
-    latency = Param.Latency('10t',
-         "Latency of the prefetcher")
+    latency = Param.Cycles('1', "Latency of the prefetcher")
     use_master_id = Param.Bool(True,
          "Use the master id to separate calculations of prefetches")
     data_accesses_only = Param.Bool(False,
diff --git a/src/mem/cache/prefetch/base.cc b/src/mem/cache/prefetch/base.cc
index f3ac5f046..be05a464f 100644
--- a/src/mem/cache/prefetch/base.cc
+++ b/src/mem/cache/prefetch/base.cc
@@ -45,7 +45,7 @@
 #include "sim/system.hh"
 
 BasePrefetcher::BasePrefetcher(const Params *p)
-    : SimObject(p), size(p->size), latency(p->latency), degree(p->degree),
+    : ClockedObject(p), size(p->size), latency(p->latency), degree(p->degree),
       useMasterId(p->use_master_id), pageStop(!p->cross_pages),
       serialSquash(p->serial_squash), onlyData(p->data_accesses_only),
       system(p->sys), masterId(system->getMasterId(name()))
@@ -212,11 +212,11 @@ BasePrefetcher::notify(PacketPtr &pkt, Tick time)
 
 
         std::list<Addr> addresses;
-        std::list<Tick> delays;
+        std::list<Cycles> delays;
         calculatePrefetch(pkt, addresses, delays);
 
         std::list<Addr>::iterator addrIter = addresses.begin();
-        std::list<Tick>::iterator delayIter = delays.begin();
+        std::list<Cycles>::iterator delayIter = delays.begin();
         for (; addrIter != addresses.end(); ++addrIter, ++delayIter) {
             Addr addr = *addrIter;
 
@@ -241,7 +241,7 @@ BasePrefetcher::notify(PacketPtr &pkt, Tick time)
             prefetch->req->setThreadContext(pkt->req->contextId(),
                                             pkt->req->threadId());
 
-            prefetch->time = time + (*delayIter); // @todo ADD LATENCY HERE
+            prefetch->time = time + clock * *delayIter;
 
             // We just remove the head if we are full
             if (pf.size() == size) {
diff --git a/src/mem/cache/prefetch/base.hh b/src/mem/cache/prefetch/base.hh
index 1517be50c..99385c1c1 100644
--- a/src/mem/cache/prefetch/base.hh
+++ b/src/mem/cache/prefetch/base.hh
@@ -41,11 +41,11 @@
 #include "base/statistics.hh"
 #include "mem/packet.hh"
 #include "params/BaseCache.hh"
-#include "sim/sim_object.hh"
+#include "sim/clocked_object.hh"
 
 class BaseCache;
 
-class BasePrefetcher : public SimObject
+class BasePrefetcher : public ClockedObject
 {
   protected:
 
@@ -64,7 +64,7 @@ class BasePrefetcher : public SimObject
     int blkSize;
 
     /** The latency before a prefetch is issued */
-    Tick latency;
+    const Cycles latency;
 
     /** The number of prefetches to issue */
     unsigned degree;
@@ -133,7 +133,7 @@ class BasePrefetcher : public SimObject
 
     virtual void calculatePrefetch(PacketPtr &pkt,
                                    std::list<Addr> &addresses,
-                                   std::list<Tick> &delays) = 0;
+                                   std::list<Cycles> &delays) = 0;
 
     std::list<PacketPtr>::iterator inPrefetch(Addr address);
 
diff --git a/src/mem/cache/prefetch/ghb.cc b/src/mem/cache/prefetch/ghb.cc
index 8e42a4e2b..9ceb051a7 100644
--- a/src/mem/cache/prefetch/ghb.cc
+++ b/src/mem/cache/prefetch/ghb.cc
@@ -40,7 +40,7 @@
 
 void
 GHBPrefetcher::calculatePrefetch(PacketPtr &pkt, std::list<Addr> &addresses,
-                                 std::list<Tick> &delays)
+                                 std::list<Cycles> &delays)
 {
     Addr blk_addr = pkt->getAddr() & ~(Addr)(blkSize-1);
     int master_id = useMasterId ? pkt->req->masterId() : 0;
diff --git a/src/mem/cache/prefetch/ghb.hh b/src/mem/cache/prefetch/ghb.hh
index ff713876a..3e4123de0 100644
--- a/src/mem/cache/prefetch/ghb.hh
+++ b/src/mem/cache/prefetch/ghb.hh
@@ -57,7 +57,7 @@ class GHBPrefetcher : public BasePrefetcher
     ~GHBPrefetcher() {}
 
     void calculatePrefetch(PacketPtr &pkt, std::list<Addr> &addresses,
-                           std::list<Tick> &delays);
+                           std::list<Cycles> &delays);
 };
 
 #endif // __MEM_CACHE_PREFETCH_GHB_PREFETCHER_HH__
diff --git a/src/mem/cache/prefetch/stride.cc b/src/mem/cache/prefetch/stride.cc
index feaa9494e..cb67f50f8 100644
--- a/src/mem/cache/prefetch/stride.cc
+++ b/src/mem/cache/prefetch/stride.cc
@@ -40,7 +40,7 @@
 
 void
 StridePrefetcher::calculatePrefetch(PacketPtr &pkt, std::list<Addr> &addresses,
-                                    std::list<Tick> &delays)
+                                    std::list<Cycles> &delays)
 {
     if (!pkt->req->hasPC()) {
         DPRINTF(HWPrefetch, "ignoring request with no PC");
diff --git a/src/mem/cache/prefetch/stride.hh b/src/mem/cache/prefetch/stride.hh
index 51b4252a1..89ac7acad 100644
--- a/src/mem/cache/prefetch/stride.hh
+++ b/src/mem/cache/prefetch/stride.hh
@@ -75,7 +75,7 @@ class StridePrefetcher : public BasePrefetcher
     ~StridePrefetcher() {}
 
     void calculatePrefetch(PacketPtr &pkt, std::list<Addr> &addresses,
-                           std::list<Tick> &delays);
+                           std::list<Cycles> &delays);
 };
 
 #endif // __MEM_CACHE_PREFETCH_STRIDE_PREFETCHER_HH__
diff --git a/src/mem/cache/prefetch/tagged.cc b/src/mem/cache/prefetch/tagged.cc
index c875b586b..f34b28b14 100644
--- a/src/mem/cache/prefetch/tagged.cc
+++ b/src/mem/cache/prefetch/tagged.cc
@@ -43,7 +43,7 @@ TaggedPrefetcher::TaggedPrefetcher(const Params *p)
 void
 TaggedPrefetcher::
 calculatePrefetch(PacketPtr &pkt, std::list<Addr> &addresses,
-                  std::list<Tick> &delays)
+                  std::list<Cycles> &delays)
 {
     Addr blkAddr = pkt->getAddr() & ~(Addr)(blkSize-1);
 
diff --git a/src/mem/cache/prefetch/tagged.hh b/src/mem/cache/prefetch/tagged.hh
index 8037196f8..a93d424e3 100644
--- a/src/mem/cache/prefetch/tagged.hh
+++ b/src/mem/cache/prefetch/tagged.hh
@@ -49,7 +49,7 @@ class TaggedPrefetcher : public BasePrefetcher
     ~TaggedPrefetcher() {}
 
     void calculatePrefetch(PacketPtr &pkt, std::list<Addr> &addresses,
-                           std::list<Tick> &delays);
+                           std::list<Cycles> &delays);
 };
 
 #endif // __MEM_CACHE_PREFETCH_TAGGED_PREFETCHER_HH__
diff --git a/src/mem/cache/tags/fa_lru.cc b/src/mem/cache/tags/fa_lru.cc
index cc2f12eef..1a607dc80 100644
--- a/src/mem/cache/tags/fa_lru.cc
+++ b/src/mem/cache/tags/fa_lru.cc
@@ -42,7 +42,7 @@
 
 using namespace std;
 
-FALRU::FALRU(unsigned _blkSize, unsigned _size, unsigned hit_latency)
+FALRU::FALRU(unsigned _blkSize, unsigned _size, Cycles hit_latency)
     : blkSize(_blkSize), size(_size), hitLatency(hit_latency)
 {
     if (!isPowerOf2(blkSize))
@@ -159,7 +159,7 @@ FALRU::invalidate(FALRU::BlkType *blk)
 }
 
 FALRUBlk*
-FALRU::accessBlock(Addr addr, int &lat, int context_src, int *inCache)
+FALRU::accessBlock(Addr addr, Cycles &lat, int context_src, int *inCache)
 {
     accesses++;
     int tmp_in_cache = 0;
diff --git a/src/mem/cache/tags/fa_lru.hh b/src/mem/cache/tags/fa_lru.hh
index 66f70a89b..19e21688c 100644
--- a/src/mem/cache/tags/fa_lru.hh
+++ b/src/mem/cache/tags/fa_lru.hh
@@ -85,7 +85,7 @@ class FALRU : public BaseTags
     /** The size of the cache. */
     const unsigned size;
     /** The hit latency of the cache. */
-    const unsigned hitLatency;
+    const Cycles hitLatency;
 
     /** Array of pointers to blocks at the cache size  boundaries. */
     FALRUBlk **cacheBoundaries;
@@ -155,7 +155,7 @@ public:
      * @param size The size of the cache.
      * @param hit_latency The hit latency of the cache.
      */
-    FALRU(unsigned blkSize, unsigned size, unsigned hit_latency);
+    FALRU(unsigned blkSize, unsigned size, Cycles hit_latency);
     ~FALRU();
 
     /**
@@ -181,7 +181,7 @@ public:
      * @param inCache The FALRUBlk::inCache flags.
      * @return Pointer to the cache block.
      */
-    FALRUBlk* accessBlock(Addr addr, int &lat, int context_src, int *inCache = 0);
+    FALRUBlk* accessBlock(Addr addr, Cycles &lat, int context_src, int *inCache = 0);
 
     /**
      * Find the block in the cache, do not update the replacement data.
@@ -205,7 +205,7 @@ public:
      * Return the hit latency of this cache.
      * @return The hit latency.
      */
-    int getHitLatency() const
+    Cycles getHitLatency() const
     {
         return hitLatency;
     }
diff --git a/src/mem/cache/tags/iic.cc b/src/mem/cache/tags/iic.cc
index 45807ef28..b9e582c29 100644
--- a/src/mem/cache/tags/iic.cc
+++ b/src/mem/cache/tags/iic.cc
@@ -220,11 +220,11 @@ IIC::regStats(const string &name)
 
 
 IICTag*
-IIC::accessBlock(Addr addr, int &lat, int context_src)
+IIC::accessBlock(Addr addr, Cycles &lat, int context_src)
 {
     Addr tag = extractTag(addr);
     unsigned set = hash(addr);
-    int set_lat;
+    Cycles set_lat;
 
     unsigned long chain_ptr = tagNull;
 
@@ -232,11 +232,11 @@ IIC::accessBlock(Addr addr, int &lat, int context_src)
         setAccess.sample(set);
 
     IICTag *tag_ptr = sets[set].findTag(tag, chain_ptr);
-    set_lat = 1;
+    set_lat = Cycles(1);
     if (tag_ptr == NULL && chain_ptr != tagNull) {
         int secondary_depth;
         tag_ptr = secondaryChain(tag, chain_ptr, &secondary_depth);
-        set_lat += secondary_depth;
+        set_lat += Cycles(secondary_depth);
         // set depth for statistics fix this later!!! egh
         sets[set].depth = set_lat;
 
@@ -250,9 +250,7 @@ IIC::accessBlock(Addr addr, int &lat, int context_src)
         }
 
     }
-    // @todo: is hashDelay is really cycles, then
-    // multiply with period
-    set_lat = set_lat * hashDelay + hitLatency;
+    set_lat = Cycles(set_lat * hashDelay + hitLatency);
     if (tag_ptr != NULL) {
         // IIC replacement: if this is not the first element of
         //   list, reorder
@@ -263,8 +261,9 @@ IIC::accessBlock(Addr addr, int &lat, int context_src)
         hitDepthTotal += sets[set].depth;
         tag_ptr->status |= BlkReferenced;
         lat = set_lat;
-        if (tag_ptr->whenReady > curTick() && tag_ptr->whenReady - curTick() > set_lat) {
-            lat = tag_ptr->whenReady - curTick();
+        if (tag_ptr->whenReady > curTick() &&
+            cache->ticksToCycles(tag_ptr->whenReady - curTick()) > set_lat) {
+            lat = cache->ticksToCycles(tag_ptr->whenReady - curTick());
         }
 
         tag_ptr->refCount += 1;
diff --git a/src/mem/cache/tags/iic.hh b/src/mem/cache/tags/iic.hh
index 97011d1c5..91e947704 100644
--- a/src/mem/cache/tags/iic.hh
+++ b/src/mem/cache/tags/iic.hh
@@ -176,7 +176,7 @@ class IIC : public BaseTags
     /** The associativity of the primary table. */
     const unsigned assoc;
     /** The base hit latency. */
-    const unsigned hitLatency;
+    const Cycles hitLatency;
     /** The subblock size, used for compression. */
     const unsigned subSize;
 
@@ -278,9 +278,9 @@ class IIC : public BaseTags
         /** The associativity of the primary table. */
         unsigned assoc;
         /** The number of cycles for each hash lookup. */
-        unsigned hashDelay;
+        Cycles hashDelay;
         /** The number of cycles to read the data. */
-        unsigned hitLatency;
+        Cycles hitLatency;
         /** The replacement policy. */
         Repl *rp;
         /** The subblock size in bytes. */
@@ -420,7 +420,7 @@ class IIC : public BaseTags
      * @param lat The access latency.
      * @return A pointer to the block found, if any.
      */
-    IICTag* accessBlock(Addr addr, int &lat, int context_src);
+    IICTag* accessBlock(Addr addr, Cycles &lat, int context_src);
 
     /**
      * Find the block, do not update the replacement data.
diff --git a/src/mem/cache/tags/lru.cc b/src/mem/cache/tags/lru.cc
index 8d32d4b35..00b13e2d8 100644
--- a/src/mem/cache/tags/lru.cc
+++ b/src/mem/cache/tags/lru.cc
@@ -116,7 +116,7 @@ LRU::~LRU()
 }
 
 LRU::BlkType*
-LRU::accessBlock(Addr addr, int &lat, int master_id)
+LRU::accessBlock(Addr addr, Cycles &lat, int master_id)
 {
     Addr tag = extractTag(addr);
     unsigned set = extractSet(addr);
@@ -128,8 +128,8 @@ LRU::accessBlock(Addr addr, int &lat, int master_id)
         DPRINTF(CacheRepl, "set %x: moving blk %x to MRU\n",
                 set, regenerateBlkAddr(tag, set));
         if (blk->whenReady > curTick()
-            && blk->whenReady - curTick() > hitLatency) {
-            lat = blk->whenReady - curTick();
+            && cache->ticksToCycles(blk->whenReady - curTick()) > hitLatency) {
+            lat = cache->ticksToCycles(blk->whenReady - curTick());
         }
         blk->refCount += 1;
     }
diff --git a/src/mem/cache/tags/lru.hh b/src/mem/cache/tags/lru.hh
index 7938fcc3c..427dba667 100644
--- a/src/mem/cache/tags/lru.hh
+++ b/src/mem/cache/tags/lru.hh
@@ -68,7 +68,7 @@ class LRU : public BaseTags
     /** The associativity of the cache. */
     const unsigned assoc;
     /** The hit latency. */
-    const unsigned hitLatency;
+    const Cycles hitLatency;
 
     /** The cache sets. */
     CacheSet *sets;
@@ -139,7 +139,7 @@ public:
      * @param lat The access latency.
      * @return Pointer to the cache block if found.
      */
-    BlkType* accessBlock(Addr addr, int &lat, int context_src);
+    BlkType* accessBlock(Addr addr, Cycles &lat, int context_src);
 
     /**
      * Finds the given address in the cache, do not update replacement data.
@@ -221,7 +221,7 @@ public:
      * Return the hit latency.
      * @return the hit latency.
      */
-    int getHitLatency() const
+    Cycles getHitLatency() const
     {
         return hitLatency;
     }