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cpu-architecture

Analogy between 2 CPU having same Instruction Set Architecture (ISA)

We have 2 CPU which has this properties-

  1. Clock Rate
  2. CPI
  3. Execution time
  4. No of instructions
  5. MIPS, will always be identical?

If 2 machines have the same Instruction Set Architecture, which of the upper mentioned property will be same?

Solution

  • 4 will be true (same dynamic instruction count) unless the program has speed-dependent behaviour (e.g. keep looping checking the time until 0.1 seconds have elapsed, or other more interesting examples you could come up with).

    No reason for 1 to be true, and it's very easy to find counter-examples if you go to any online computer store and look at different models of the same generation of x86-64 CPUs with different max clock speeds. And across different generations, there can be even larger differences in clock speed, e.g. a 25MHz 80386 vs. a 5GHz Zen 2 or Coffee Lake.