[data from a 1.0 GHz Pentium III (Coppermine)]

PERFCTR INIT: vendor 0, family 6, model 8, stepping 6, clock 999784 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 90 cycles
PERFCTR INIT: rdtsc cost is 32.4 cycles (2165 total)
PERFCTR INIT: rdpmc cost is 35.4 cycles (2357 total)
PERFCTR INIT: rdmsr (counter) cost is 91.4 cycles (5943 total)
PERFCTR INIT: rdmsr (evntsel) cost is 72.8 cycles (4755 total)
PERFCTR INIT: wrmsr (counter) cost is 80.7 cycles (5258 total)
PERFCTR INIT: wrmsr (evntsel) cost is 76.1 cycles (4963 total)
PERFCTR INIT: read cr4 cost is 1.9 cycles (217 total)
PERFCTR INIT: write cr4 cost is 42.2 cycles (2795 total)
perfctr: driver 2.3.2, cpu type Intel Pentium III at 999784 kHz
