Measuring CPU speeds ( was RE: Why isn't Apple releasing patches for the Month of Apple )

Jim Leonard wrote: It's the fastest clock you can claim to have anywhere in your machine while keeping a straight face :-) Acually, to be fair, manufacturers weren't quite that bad (usually) but identifying the fastest clock is actually quite hard, even if you are trying to be honest! As CPU cycle times dropped, it was quite often the case that the external clock might be running at say 20MHz so that the rest of the slow external world could keep up but that was doubled inside the chip to perhaps 40MHz. In other cases the external clock might be quite high but would be split internally to provide the phases required to clock the various CPU stages. Sometimes the manufacturer would publish a cycle time, but as pipelined architectures came to the fore those cycle times became less useful, so then they started to publish instructions per tick or clocks per instruction. Antonio