To know the clock frequency of an IBM Power processor in AIX run pmcycles
root@aix:/ # pmcycles
This machine runs at 1200 MHz
To know the individual frequency of each processor, run pmcycles -m
root@aix:/ # pmcycles -m
CPU 0 runs at 1200 MHz
CPU 1 runs at 1200 MHz
CPU 2 runs at 1200 MHz
CPU 3 runs at 1200 MHz