[data from a 1.2 GHz Athlon]

PERFCTR INIT: vendor 2, family 6, model 4, stepping 2, clock 1200062 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 85 cycles
PERFCTR INIT: rdtsc cost is 10.7 cycles (773 total)
PERFCTR INIT: rdpmc cost is 18.6 cycles (1280 total)
PERFCTR INIT: rdmsr (counter) cost is 59.9 cycles (3919 total)
PERFCTR INIT: rdmsr (evntsel) cost is 52.4 cycles (3441 total)
PERFCTR INIT: wrmsr (counter) cost is 79.8 cycles (5198 total)
PERFCTR INIT: wrmsr (evntsel) cost is 231.8 cycles (14925 total)
PERFCTR INIT: read cr4 cost is 9.8 cycles (715 total)
PERFCTR INIT: write cr4 cost is 63.1 cycles (4129 total)
perfctr: driver 2.3.10, cpu type AMD K7 at 1200062 kHz