[data from an 850 Mhz Athlon]

PERFCTR INIT: vendor 2, family 6, model 4, stepping 2, clock 850063 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 90 cycles
PERFCTR INIT: rdtsc cost is 15.2 cycles (1064 total)
PERFCTR INIT: rdpmc cost is 13.3 cycles (947 total)
PERFCTR INIT: rdmsr (counter) cost is 51.5 cycles (3391 total)
PERFCTR INIT: rdmsr (evntsel) cost is 52.6 cycles (3458 total)
PERFCTR INIT: wrmsr (counter) cost is 79.7 cycles (5191 total)
PERFCTR INIT: wrmsr (evntsel) cost is 231.8 cycles (14928 total)
PERFCTR INIT: read cr4 cost is 7.0 cycles (540 total)
PERFCTR INIT: write cr4 cost is 62.9 cycles (4121 total)
perfctr: driver 2.3.4, cpu type AMD K7 at 850063 kHz