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# Copyright (c) 2020 ARM Limited
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#
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# to a hardware implementation of the functionality of the software
# licensed hereunder. You may use the software subject to the license
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#
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# redistributions in binary form must reproduce the above copyright
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# this software without specific prior written permission.
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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from m5.params import *
from m5.proxy import *
from m5.objects.MemCtrl import MemCtrl
from m5.objects.MemInterface import MemInterface
from m5.objects.DRAMInterface import AddrMap
# The following interface aims to model byte-addressable NVM
# The most important system-level performance effects of a NVM
# are modeled without getting into too much detail of the media itself.
class NVMInterface(MemInterface):
type = "NVMInterface"
cxx_header = "mem/nvm_interface.hh"
cxx_class = "gem5::memory::NVMInterface"
# NVM DIMM could have write buffer to offload writes
# define buffer depth, which will limit the number of pending writes
max_pending_writes = Param.Unsigned("1", "Max pending write commands")
# NVM DIMM could have buffer to offload read commands
# define buffer depth, which will limit the number of pending reads
max_pending_reads = Param.Unsigned("1", "Max pending read commands")
# timing behaviour and constraints - all in nanoseconds
# define average latency for NVM media. Latency defined uniquely
# for read and writes as the media is typically not symmetric
tREAD = Param.Latency("100ns", "Average NVM read latency")
tWRITE = Param.Latency("200ns", "Average NVM write latency")
tSEND = Param.Latency("15ns", "Access latency")
two_cycle_rdwr = Param.Bool(
False, "Two cycles required to send read and write commands"
)
def controller(self):
"""
Instantiate the memory controller and bind it to
the current interface.
"""
controller = MemCtrl()
controller.dram = self
return controller
# NVM delays and device architecture defined to mimic PCM like memory.
# Can be configured with DDR4_2400 sharing the channel
class NVM_2400_1x64(NVMInterface):
write_buffer_size = 128
read_buffer_size = 64
max_pending_writes = 128
max_pending_reads = 64
device_rowbuffer_size = "256B"
# 8X capacity compared to DDR4 x4 DIMM with 8Gb devices
device_size = "512GiB"
# Mimic 64-bit media agnostic DIMM interface
device_bus_width = 64
devices_per_rank = 1
ranks_per_channel = 1
banks_per_rank = 16
burst_length = 8
two_cycle_rdwr = True
# 1200 MHz
tCK = "0.833ns"
tREAD = "150ns"
tWRITE = "500ns"
tSEND = "14.16ns"
tBURST = "3.332ns"
# Default all bus turnaround and rank bus delay to 2 cycles
# With DDR data bus, clock = 1200 MHz = 1.666 ns
tWTR = "1.666ns"
tRTW = "1.666ns"
tCS = "1.666ns"