For information:
I found the following document useful when trying to
understand the PC timers:
ftp://cogito.lscp.ehess.fr/pub/expe6/misc/pctim003.zip
The rtc.txt file in the documentation of the linux kernel is also an
interesting read.
To assess the timing of several programs (with millisecond
precision, not microsecond), I’ve set up a system which uses a laplink
parallel port to parallel port cable between to
PCs. One runs a MSDOS program which logs and timestamps all events
arriving to the parallel port, with millisecond precision.
The other computer runs the piece of
software of interest, which must toggle bitson the parallel port at
the moments of interest.
I found it quite useful to detect latencies of a few milliseconds, in
programs meant to use SDL for stimulus presentation.
I described the system at:
http://www.pallier.org/ressources/timelpt/timelpt.html
Christophe Pallier