diff options
Diffstat (limited to 'src/mem/simple_dram.cc')
| -rw-r--r-- | src/mem/simple_dram.cc | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/src/mem/simple_dram.cc b/src/mem/simple_dram.cc index 6885e48c0..32a13eef0 100644 --- a/src/mem/simple_dram.cc +++ b/src/mem/simple_dram.cc @@ -166,6 +166,11 @@ SimpleDRAM::writeQueueFull() const SimpleDRAM::DRAMPacket* SimpleDRAM::decodeAddr(PacketPtr pkt) { + // decode the address based on the address mapping scheme + // + // with R, C, B and K denoting rank, column, bank and rank, + // respectively, and going from MSB to LSB, the two schemes are + // RKBC (openmap) and RCKB (closedmap) uint8_t rank; uint16_t bank; uint16_t row; @@ -176,26 +181,46 @@ SimpleDRAM::decodeAddr(PacketPtr pkt) // truncate the address to the access granularity addr = addr / bytesPerCacheLine; + // we have removed the lowest order address bits that denote the + // position within the cache line, proceed and select the + // appropriate bits for bank, rank and row (no column address is + // needed) if (addrMapping == Enums::openmap) { + // the lowest order bits denote the column to ensure that + // sequential cache lines occupy the same row addr = addr / linesPerRowBuffer; + // after the column bits, we get the bank bits to interleave + // over the banks bank = addr % banksPerRank; addr = addr / banksPerRank; + // after the bank, we get the rank bits which thus interleaves + // over the ranks rank = addr % ranksPerChannel; addr = addr / ranksPerChannel; + // lastly, get the row bits row = addr % rowsPerBank; addr = addr / rowsPerBank; } else if (addrMapping == Enums::closemap) { + // optimise for closed page mode and utilise maximum + // parallelism of the DRAM (at the cost of power) + + // start with the bank bits, as this provides the maximum + // opportunity for parallelism between requests bank = addr % banksPerRank; addr = addr / banksPerRank; + // next get the rank bits rank = addr % ranksPerChannel; addr = addr / ranksPerChannel; + // next the column bits which we do not need to keep track of + // and simply skip past addr = addr / linesPerRowBuffer; + // lastly, get the row bits row = addr % rowsPerBank; addr = addr / rowsPerBank; } else |