[data from a 1.66 GHz Athlon XP 2000+]

PERFCTR INIT: vendor 2, family 6, model 6, stepping 2, clock 1679042 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 157 cycles
PERFCTR INIT: rdtsc cost is 14.0 cycles (1054 total)
PERFCTR INIT: rdpmc cost is 14.9 cycles (1113 total)
PERFCTR INIT: rdmsr (counter) cost is 51.7 cycles (3472 total)
PERFCTR INIT: rdmsr (evntsel) cost is 52.6 cycles (3526 total)
PERFCTR INIT: wrmsr (counter) cost is 82.9 cycles (5463 total)
PERFCTR INIT: wrmsr (evntsel) cost is 231.9 cycles (14999 total)
PERFCTR INIT: read cr4 cost is 4.7 cycles (464 total)
PERFCTR INIT: write cr4 cost is 62.8 cycles (4180 total)
PERFCTR INIT: sync_core cost is 73.9 cycles (4887 total)
perfctr: driver 2.7.8, cpu type AMD K7/K8 at 1679042 kHz

PERFCTR INIT: vendor 2, family 6, model 6, stepping 2, clock 1659642 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 236 cycles
PERFCTR INIT: rdtsc cost is 17.1 cycles (1336 total)
PERFCTR INIT: rdpmc cost is 15.4 cycles (1225 total)
PERFCTR INIT: rdmsr (counter) cost is 49.4 cycles (3402 total)
PERFCTR INIT: rdmsr (evntsel) cost is 50.2 cycles (3455 total)
PERFCTR INIT: wrmsr (counter) cost is 83.3 cycles (5573 total)
PERFCTR INIT: wrmsr (evntsel) cost is 229.6 cycles (14936 total)
PERFCTR INIT: read cr4 cost is 0.1 cycles (245 total)
PERFCTR INIT: write cr4 cost is 60.7 cycles (4124 total)
PERFCTR INIT: write LVTPC cost is 3.0 cycles (432 total)
perfctr: driver 2.6.6, cpu type AMD K7 at 1659642 kHz