Getting Time Difference

["Gilad Benjamini" <yaelgilad@myrealbox.com>]

Hi,
I am porting code from a x86 platform.
That code uses rdtsc and cpu_khz to compute
the time difference between two events. Jiffies aren't good enough in this 
case.

Looking through header files I can find a few MIPS replacements.
What is the "right" one to use ?

What is the best way to change the code so it can compile
and run on both platforms ?