about interrupt latency

[Francesco Oppedisano <francesco.oppedisano@gmail.com>]

Hi,
i'm trying to estimate the interrupt latency (time between hardware
interrrupt and the start of the ISR) of a linux kernel 2.4.29 and i
used a simple tecnique: inside the do_timer_interrupt i read the 8259
counter to obtain the elapsed time.
By this mean i found a latency of about 6/7 microseconds that is very
similar to the time measured in some articles but with CPU much slower
while i expected the latency was shorter on faster CPUs.
So, my questions are: 
1)what's the depency between the interrupt latency and the CPU speed?
2)what are the factors at the origin of th interrupt latency?

Than u very much

Francesco Oppedisano