Approximate Number of CPU Cycles for Various Operations

reference citations cpu-cycles
colordot picture colordot · Apr 24, 2010 · Viewed 15.7k times · Source

I am trying to find a reference for approximately how many CPU cycles various operations require.

I don't need exact numbers (as this is going to vary between CPUs) but I'd like something relatively credible that gives ballpark figures that I could cite in discussion with friends.

As an example, we all know that floating point division takes more CPU cycles than say doing a bitshift.

I'd guess that the difference is that the division is around 100 cycles, where as a shift is 1 but I'm looking for something to cite to back that up.

Can anyone recommend such a resource?

Answer

nos picture nos · Apr 24, 2010

For x86 processors, see Intel® 64 and IA-32 Architectures Optimization Reference Manual, probably Appendix C.

However, it's not in any way easy to figure out how many cycles an instruction takes to execute on a modern x86 processor, as it depends too much on e.g. accessing data in cache,aligned access, whether branch prediction fails, if there's a stall in the instruction pipeline and quite a lot of other things.

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