> However if you need no jitter on a PC that has the most powerfull
> Pentium cpu, and are willing to loose a lot of performances, an idea
> pointed to me by Tomasz Motyleski can be the right one: interrupt at a
> time before the needed one, according to the max jitter you have
> measured, keeping the interrupts disabled, and keep reading the cpu
> clock (TSC) till the very instant you are waiting for. In that way the
> jitter is less than 1 us. After Tomasz's suggestion I tried it under
> RTAI, it works nicely but sucks a lot.
The MARUTI operating system group at U maryland has been doing that. In
addition to an early interrupt, they also ensure that the time
critical code is preloaded into the cache by the first interrupt, and
then go into a busy wait till the exact time.
However, they have a peak jitter of close to 2us. But it was 75ns in most
cases.(15clocks on a 200mhz ppro)
manoj
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