how to get consistent cpu timings on this processor of T41

[T400plus]

I have set my T41 to run at fixed 1.7 , maximum performance.Then why do my
program execution time vary between 0.77 and 0.81 seconds .
I have 1.5GB memory , and No I/O. Dothan procesor 1.7 GHZ(735).
I am a sometime developer.

[Harryc]

First, how would you even measure 1/10 of a second? Second, why does 1/10 of a second matter to you? Third, how do you know the CPU is responsible for this 1/10 of a second delay? If your program is running on top of an OS, that is not a constant (not even close) environment.

[T400plus]

I am using the c runtime function ..
Actually I am comparing 2 algorithms which are 1:2 approx.
But the variations are making me weep over my effort.

I initially presumed it is because the frequency is
shifting internally ,so I set it to maximum performance.
The only other programs are NHC and Avira .I will disable them and check again.