Is IPC (Instructions per Cycle) a good measure of performance for an x86 processor?
NO. Because one x86 instruction may be broken up into numerous uops, it is never appropriate to compare IPC figures for committed x86 instructions per clock with IPC values from a RISC machine. Furthermore, different x86 implementations use varying numbers of uops per x86 instruction as a matter of encoding, so even comparing the uop based IPC between x86 implementations or RISC-like machines is inaccurate. Users are strongly advised to use relative performance measures instead. Comparing the total simulated cycle count required to complete a given benchmark between different simulator configurations is much more appropriate. An example would be “the baseline took 100M cycles, while our improved system took 50M cycles, for a 2x improvement.
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