[data from a 3.0 GHz Pentium 4]

PERFCTR INIT: vendor 0, family 15, model 2, stepping 7, clock 3057662 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 264 cycles
PERFCTR INIT: rdtsc cost is 77.5 cycles (5228 total)
PERFCTR INIT: rdpmc cost is 146.2 cycles (9624 total)
PERFCTR INIT: rdmsr (counter) cost is 255.0 cycles (16584 total)
PERFCTR INIT: rdmsr (escr) cost is 166.2 cycles (10904 total)
PERFCTR INIT: wrmsr (counter) cost is 794.4 cycles (51108 total)
PERFCTR INIT: wrmsr (escr) cost is 874.0 cycles (56204 total)
PERFCTR INIT: read cr4 cost is 5.1 cycles (592 total)
PERFCTR INIT: write cr4 cost is 258.8 cycles (16828 total)
PERFCTR INIT: rdpmc (fast) cost is 60.5 cycles (4136 total)
PERFCTR INIT: rdmsr (cccr) cost is 167.0 cycles (10952 total)
PERFCTR INIT: wrmsr (cccr) cost is 833.9 cycles (53636 total)
perfctr: driver 2.6.0 DEBUG, cpu type Intel Pentium 4 Model 2 at 3057662 kHz
