[data from a 1.8GHz Mobile P4-M]

PERFCTR INIT: vendor 0, family 15, model 2, stepping 7, clock 1789893 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 292 cycles
PERFCTR INIT: rdtsc cost is 81.8 cycles (5528 total)
PERFCTR INIT: rdpmc cost is 145.8 cycles (9628 total)
PERFCTR INIT: rdmsr (counter) cost is 254.5 cycles (16580 total)
PERFCTR INIT: rdmsr (escr) cost is 165.8 cycles (10904 total)
PERFCTR INIT: wrmsr (counter) cost is 792.8 cycles (51032 total)
PERFCTR INIT: wrmsr (escr) cost is 872.6 cycles (56144 total)
PERFCTR INIT: read cr4 cost is 4.6 cycles (588 total)
PERFCTR INIT: write cr4 cost is 253.4 cycles (16512 total)
PERFCTR INIT: rdpmc (fast) cost is 60.3 cycles (4152 total)
PERFCTR INIT: rdmsr (cccr) cost is 166.5 cycles (10952 total)
PERFCTR INIT: wrmsr (cccr) cost is 832.8 cycles (53592 total)
perfctr: driver 2.7.3, cpu type Intel P4 at 1789893 kHz