Memory Subsystem DesignorNothing Beats Cold, Hard CacheCSE 240ADean TullsenWho Cares about Memory Hierarchy?•Processor Only Thus Far in CourseCPU DRAM GCPU-DRAM Gap1980: no cache in μproc; 1995 2 level cache 60% trans on Alpha 21164 μprocCSE 240ADean Tullsen1995 2-level cache, 60% trans. on Alpha 21164 μprocMemory Cache•Can put small, fastmemory close tomemory close to processor.•What do we put there?cpucachememoryCSE 240ADean TullsenMemory Locality•Memory hierarchies take advantage of memory locality. •Memory locality is the principle that future memory accesses are nearpast accesses.•Memory hierarchies take advantage of two types ofMemory hierarchies take advantage of two types of locality–Temporal locality-- near in time => we will often access the same didata again very soon–Spatial locality-- near in space/distance => our next access is often very close to our last access (or recent accesses).1,2,3,1,2,3,8,8,47,9,10,8,8...CSE 240ADean Tullsen
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