RDTSC reliable for use by clockspeed?

Hi there,

Various sources now say that RDTSC is no longer a reliable clock
for clockspeed due to power-mode adjustments and non-sync on
newer multi-core machines.

Will this affect clockspeed?

On Solaris, according to the man pages, gethrtime() is the same as
clock_gettime(CLOCK_MONOTONIC,...) and seems to be based on
a hardware clock.

On Linux, is clock_gettime(CLOCK_MONOTONIC,...) a good choice?

(POSIX says that CLOCK_MONOTONIC is merely monotonic and
does not have steps. It does not say it should be based on a hardware
clock like the 82C54.)

Does anyone know of other OS-specific ops that can be used to
get hardware-clock-based timing info that can replace the RDTSC
macro in the clockspeed source?

Many thanks

-paul