[data from a 2.0 GHz Opteron 246]

PERFCTR INIT: vendor 2, family 15, model 5, stepping 8, clock 1992598 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 609 cycles
PERFCTR INIT: rdtsc cost is 4.0 cycles (865 total)
PERFCTR INIT: rdpmc cost is 3.6 cycles (840 total)
PERFCTR INIT: rdmsr (counter) cost is 42.7 cycles (3342 total)
PERFCTR INIT: rdmsr (evntsel) cost is 49.3 cycles (3768 total)
PERFCTR INIT: wrmsr (counter) cost is 63.7 cycles (4686 total)
PERFCTR INIT: wrmsr (evntsel) cost is 323.6 cycles (21321 total)
PERFCTR INIT: read cr4 cost is 6710884.1 cycles (464 total)
PERFCTR INIT: write cr4 cost is 58.7 cycles (4370 total)
PERFCTR INIT: write LVTPC cost is 5.2 cycles (944 total)
perfctr: driver 2.6.8, cpu type AMD K8C at 1992598 kHz