[data from a 3.4 GHz Pentium 4 Model 4]

PERFCTR INIT: vendor 0, family 15, model 4, stepping 1, clock 3393806 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 825 cycles
PERFCTR INIT: rdtsc cost is 96.8 cycles (7021 total)
PERFCTR INIT: rdpmc cost is 236.0 cycles (15929 total)
PERFCTR INIT: rdmsr (counter) cost is 348.8 cycles (23154 total)
PERFCTR INIT: rdmsr (escr) cost is 367.6 cycles (24353 total)
PERFCTR INIT: wrmsr (counter) cost is 990.3 cycles (64209 total)
PERFCTR INIT: wrmsr (escr) cost is 1023.8 cycles (66351 total)
PERFCTR INIT: read cr4 cost is 19.2 cycles (2057 total)
PERFCTR INIT: write cr4 cost is 391.6 cycles (25891 total)
PERFCTR INIT: rdpmc (fast) cost is 94.8 cycles (6893 total)
PERFCTR INIT: rdmsr (cccr) cost is 377.0 cycles (24956 total)
PERFCTR INIT: wrmsr (cccr) cost is 977.8 cycles (63410 total)
PERFCTR INIT: write LVTPC cost is 28.5 cycles (2652 total)
PERFCTR INIT: sync_core cost is 421.1 cycles (27778 total)
perfctr: driver 2.7.6, cpu type Intel P4 at 3393806 kHz