[data from a 166MHz Pentium MMX]

PERFCTR INIT: vendor 0, family 5, model 4, stepping 3, clock 166590 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 56 cycles
PERFCTR INIT: rdtsc cost is 9.1 cycles (640 total)
PERFCTR INIT: rdpmc cost is 13.8 cycles (944 total)
PERFCTR INIT: rdmsr (counter) cost is 28.1 cycles (1860 total)
PERFCTR INIT: rdmsr (evntsel) cost is 23.8 cycles (1583 total)
PERFCTR INIT: wrmsr (counter) cost is 36.0 cycles (2362 total)
PERFCTR INIT: wrmsr (evntsel) cost is 36.3 cycles (2385 total)
PERFCTR INIT: read %cr4 cost is 4.0 cycles (312 total)
PERFCTR INIT: write %cr4 cost is 17.0 cycles (1149 total)
perfctr: driver 2.0-pre5, cpu type Intel Pentium MMX at 166590 kHz