[data from a 2.66 GHz Intel Core i7-920]

PERFCTR INIT: vendor 0, family 6, model 26, stepping 4, clock 2698926 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 290 cycles
PERFCTR INIT: rdtsc cost is 22.4 cycles (1725 total)
PERFCTR INIT: rdpmc cost is 32.1 cycles (2350 total)
PERFCTR INIT: rdmsr (counter) cost is 106.5 cycles (7111 total)
PERFCTR INIT: rdmsr (evntsel) cost is 87.3 cycles (5879 total)
PERFCTR INIT: wrmsr (counter) cost is 160.9 cycles (10592 total)
PERFCTR INIT: wrmsr (evntsel) cost is 150.2 cycles (9908 total)
PERFCTR INIT: read cr4 cost is 9.6 cycles (906 total)
PERFCTR INIT: write cr4 cost is 113.5 cycles (7555 total)
PERFCTR INIT: write LVTPC cost is 26.2 cycles (1968 total)
PERFCTR INIT: sync_core cost is 186.3 cycles (12219 total)
PERFCTR INIT: read fixed_ctr0 cost is 31.4 cycles (2302 total)
PERFCTR INIT: wrmsr fixed_ctr_ctrl cost is 158.6 cycles (10441 total)
perfctr: driver 2.6.40, cpu type Intel Core i7 at 2698926 kHz