Calculating the effect of the cache on the overall CPI of the processor

Question

How does one calculate the effect of L1 and L2 cache\'s on the overall CPI of the processor given base CPI, miss rate % of L1 and L2 caches and access times of L1, L2, and the m

Answer 1

I think you are not taking into account the Average Number of Memory Accesses per Instruction (AMAPI).

For example, if there are 30% of load/store instructions, this number would be 1.3 (one access to fetch the instruction and 0.3 due to memory access instructions)

So

CPI = BaseCPI + (AMAT - ideal memory access time) x AMAPI

Being AMAT the Average Memory Access Time. For a two-level hierarcchy:

AMAT = L1_hit_latency + L1_miss_rate x (L2_hit_latency + L2_miss_rate x Main_Memory_latency)