[data from a 2.2 GHz Pentium 4 Xeon (Northwood)]

PERFCTR INIT: vendor 0, family 15, model 2, stepping 4, clock 2199807 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 248 cycles
PERFCTR INIT: rdtsc cost is 82.8 cycles (5548 total)
PERFCTR INIT: rdpmc cost is 143.3 cycles (9424 total)
PERFCTR INIT: rdmsr (counter) cost is 251.4 cycles (16340 total)
PERFCTR INIT: rdmsr (escr) cost is 166.4 cycles (10900 total)
PERFCTR INIT: wrmsr (counter) cost is 842.0 cycles (54136 total)
PERFCTR INIT: wrmsr (escr) cost is 912.6 cycles (58660 total)
PERFCTR INIT: read cr4 cost is 4.8 cycles (556 total)
PERFCTR INIT: write cr4 cost is 255.3 cycles (16592 total)
PERFCTR INIT: rdpmc (fast) cost is 60.4 cycles (4116 total)
PERFCTR INIT: rdmsr (cccr) cost is 167.3 cycles (10960 total)
PERFCTR INIT: wrmsr (cccr) cost is 865.0 cycles (55612 total)
perfctr: driver 2.3.12, cpu type Intel Pentium 4 Model 2 at 2199807 kHz