[data from a 2.26 GHz Pentium 4 (Northwood)]

PERFCTR INIT: vendor 0, family 15, model 2, stepping 4, clock 2292182 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 228 cycles
PERFCTR INIT: rdtsc cost is 78.5 cycles (5252 total)
PERFCTR INIT: rdpmc cost is 143.8 cycles (9436 total)
PERFCTR INIT: rdmsr (counter) cost is 251.7 cycles (16340 total)
PERFCTR INIT: rdmsr (escr) cost is 166.8 cycles (10904 total)
PERFCTR INIT: wrmsr (counter) cost is 841.3 cycles (54072 total)
PERFCTR INIT: wrmsr (escr) cost is 914.1 cycles (58736 total)
PERFCTR INIT: read cr4 cost is 5.1 cycles (560 total)
PERFCTR INIT: write cr4 cost is 253.3 cycles (16444 total)
PERFCTR INIT: rdpmc (fast) cost is 58.8 cycles (3992 total)
PERFCTR INIT: rdmsr (cccr) cost is 168.0 cycles (10980 total)
PERFCTR INIT: wrmsr (cccr) cost is 864.9 cycles (55584 total)
perfctr: driver 2.5.1, cpu type Intel Pentium 4 Model 2 at 2292182 kHz