Question

Calculate the performance of a processor taking into account stalls due to data cache and instruction cache misses. The data cache (for loads and stores) is the same as described previously and 30% of instructions are loads and stores. The instruction cache has a hit rate of 90% with a miss penalty of 50 cycles and hit time is 1 cycle. Assume the base CPI using a perfect memory system is 1.0. Calculate the CPI of the pipeline, assuming everything else is working perfectly. Assume the load never stalls a dependent instruction and assume the processor must wait for stores to finish when they miss the cache. Finally, assume that instruction cache misses and data cache misses never occur at the same time.

Answer 1

Answer:

- Calculate the additional CPI due to the icache stalls.

- Calculate the additional CPI due to the dcache stalls.  

- Calculate the overall CPI for the machine.

The additional CPI due to icache stalls = Hit Rate * Hit Latency + Miss Rate*  

Miss Penalty = 0.9*2 + 0.1*50 = 1.8 + 5 = 6.8  

The additional CPI due to dcache stalls = 0.92*2 + 0.08*124 = 11.76  

The overall CPI = 0.3*11.76 + 0.7*1.0 + 1.0*6.8 = 11.03 7.  

Explanation: