[data from an Athlon XP-M 2500+]

PERFCTR INIT: vendor 2, family 6, model 10, stepping 0, clock 2205427 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 99 cycles
PERFCTR INIT: rdtsc cost is 15.3 cycles (1084 total)
PERFCTR INIT: rdpmc cost is 11.6 cycles (842 total)
PERFCTR INIT: rdmsr (counter) cost is 51.8 cycles (3415 total)
PERFCTR INIT: rdmsr (evntsel) cost is 52.5 cycles (3465 total)
PERFCTR INIT: wrmsr (counter) cost is 79.9 cycles (5214 total)
PERFCTR INIT: wrmsr (evntsel) cost is 231.6 cycles (14923 total)
PERFCTR INIT: read cr4 cost is 2.1 cycles (234 total)
PERFCTR INIT: write cr4 cost is 65.1 cycles (4271 total)
PERFCTR INIT: write LVTPC cost is 5.1 cycles (428 total)
perfctr: driver 2.7.3, cpu type AMD K7/K8 at 2205427 kHz