[data from a 200MHz Pentium Pro]

PERFCTR INIT: vendor 0, family 6, model 1, stepping 9, clock 199312 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 88 cycles
PERFCTR INIT: rdtsc cost is 36.0 cycles (2396 total)
PERFCTR INIT: rdpmc cost is 33.1 cycles (2209 total)
PERFCTR INIT: rdmsr (counter) cost is 81.1 cycles (5280 total)
PERFCTR INIT: rdmsr (evntsel) cost is 68.4 cycles (4470 total)
PERFCTR INIT: wrmsr (counter) cost is 82.3 cycles (5357 total)
PERFCTR INIT: wrmsr (evntsel) cost is 73.0 cycles (4760 total)
PERFCTR INIT: read %cr4 cost is 1.9 cycles (211 total)
PERFCTR INIT: write %cr4 cost is 38.2 cycles (2537 total)
perfctr: driver 2.0-pre6, cpu type Intel Pentium Pro at 199312 kHz
