*Nix4all

You can use lsattr to list CPU info

(this is an example from a real AIX machine)
# lsattr -E -l proc0

frequency 4204000000
smt_enabled true
smt_threads 2
state enable
type PowerPC_POWER6

And after version 5.1 AIX also supports this

(again same real aix machine :) )
# pmcycles
This machine runs at 4204 MHz