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I was very confused how to solve the problem when there are two levels of cache, My doubt is how does we quantify the performance when there are two caches. Consider a problem like this

Cache L1 access time of main memory = T1 and miss rate = X%.

Cache L2 access time of main memory = T2 and miss rate = Y%.

CPI of processor without memory stalls is C. and clock rate is fGHz.

How much faster the performance be after adding L2 cache?

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  • $\begingroup$ There is a blatant problem here: L1 cache would be faster and smaller than L2 cache, and L1 cache misses are often filled from L2 cache, not main memory. $\endgroup$
    – gnasher729
    Feb 20, 2022 at 21:45
  • $\begingroup$ If we approximate that all the miss rates are independent, we can calculate the average memory access time with and without the L2 cache. Hint: Misses in the L1 cache go to the L2 cache, which can hit or miss. $\endgroup$
    – user253751
    Apr 25, 2022 at 9:50

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