[data from a 1.4 GHz Opteron]

PERFCTR INIT: vendor 2, family 15, model 5, stepping 0, clock 1381091 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 80 cycles
PERFCTR INIT: rdtsc cost is 6.1 cycles (474 total)
PERFCTR INIT: rdpmc cost is 14.1 cycles (983 total)
PERFCTR INIT: rdmsr (counter) cost is 50.9 cycles (3343 total)
PERFCTR INIT: rdmsr (evntsel) cost is 57.6 cycles (3769 total)
PERFCTR INIT: wrmsr (counter) cost is 68.9 cycles (4495 total)
PERFCTR INIT: wrmsr (evntsel) cost is 320.6 cycles (20602 total)
PERFCTR INIT: read cr4 cost is 6.9 cycles (526 total)
PERFCTR INIT: write cr4 cost is 66.0 cycles (4307 total)
perfctr: disabled lapic_nmi_watchdog
perfctr: driver 2.5.2 DEBUG, cpu type AMD K8 at 1381091 kHz