>From Linus Torvalds, torvalds@cc.helsinki.fi, explaining about the
variation one may see in the BogoMips rating, in c.o.l.development,
at 28 April 1994
`The BogoMips calculation loop is "quantizised", so you're most likely to get the exact same number all the time. You usually will get different numbers only if the speed is just on the "edge", when small variations (different time for interrupt ticks etc) will make it jump from one value to the other.'
If a kernel is not compiled specifically for the pertaining CPU, also some (even large) variations of the BogoMips ratings can occur, mainly due to erroneous alignment. This problem apparently only occurs on the various x86 CPUs (Intel and clones). Fortunately it can easily be solved: recompile the kernel specifically for your CPU.
Note that the BogoMips algorithm, contrarily to popular believe, did NOT change significantly over the various kernel versions.