[data from a 1.5 GHz Pentium 4 (Willamette)]

PERFCTR INIT: vendor 0, family 15, model 1, stepping 2, clock 1495172 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 224 cycles
PERFCTR INIT: rdtsc cost is 78.0 cycles (5220 total)
PERFCTR INIT: rdpmc cost is 143.1 cycles (9388 total)
PERFCTR INIT: rdmsr (counter) cost is 247.6 cycles (16072 total)
PERFCTR INIT: rdmsr (escr) cost is 162.6 cycles (10636 total)
PERFCTR INIT: wrmsr (counter) cost is 817.6 cycles (52552 total)
PERFCTR INIT: wrmsr (escr) cost is 877.0 cycles (56352 total)
PERFCTR INIT: read cr4 cost is 5.1 cycles (552 total)
PERFCTR INIT: write cr4 cost is 245.3 cycles (15924 total)
PERFCTR INIT: rdpmc (fast) cost is 59.3 cycles (4020 total)
PERFCTR INIT: rdmsr (cccr) cost is 163.6 cycles (10696 total)
PERFCTR INIT: wrmsr (cccr) cost is 833.3 cycles (53560 total)
perfctr: driver 2.3.4, cpu type Intel Pentium 4 at 1495172 kHz