[data from a 2.4 GHz Pentium 4 Xeon (Northwood)]

PERFCTR INIT: vendor 0, family 15, model 2, stepping 4, clock 2392322 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 276 cycles
PERFCTR INIT: rdtsc cost is 84.4 cycles (5680 total)
PERFCTR INIT: rdpmc cost is 148.1 cycles (9760 total)
PERFCTR INIT: rdmsr (counter) cost is 251.0 cycles (16340 total)
PERFCTR INIT: rdmsr (escr) cost is 165.8 cycles (10892 total)
PERFCTR INIT: wrmsr (counter) cost is 848.8 cycles (54600 total)
PERFCTR INIT: wrmsr (escr) cost is 920.3 cycles (59176 total)
PERFCTR INIT: read cr4 cost is 4.3 cycles (556 total)
PERFCTR INIT: write cr4 cost is 252.6 cycles (16444 total)
PERFCTR INIT: rdpmc (fast) cost is 60.0 cycles (4116 total)
PERFCTR INIT: rdmsr (cccr) cost is 166.9 cycles (10960 total)
PERFCTR INIT: wrmsr (cccr) cost is 872.5 cycles (56120 total)
perfctr: driver 2.3.11, cpu type Intel Pentium 4 Model 2 at 2392322 kHz

PERFCTR INIT: vendor 0, family 15, model 2, stepping 9, clock 2405401 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 304 cycles
PERFCTR INIT: rdtsc cost is 76.8 cycles (5224 total)
PERFCTR INIT: rdpmc cost is 145.6 cycles (9628 total)
PERFCTR INIT: rdmsr (counter) cost is 254.5 cycles (16592 total)
PERFCTR INIT: rdmsr (escr) cost is 165.6 cycles (10908 total)
PERFCTR INIT: wrmsr (counter) cost is 801.8 cycles (51620 total)
PERFCTR INIT: wrmsr (escr) cost is 1112.6 cycles (71516 total)
PERFCTR INIT: read cr4 cost is 4.0 cycles (560 total)
PERFCTR INIT: write cr4 cost is 255.0 cycles (16624 total)
PERFCTR INIT: rdpmc (fast) cost is 59.1 cycles (4092 total)
PERFCTR INIT: rdmsr (cccr) cost is 166.4 cycles (10956 total)
PERFCTR INIT: wrmsr (cccr) cost is 838.4 cycles (53964 total)
PERFCTR INIT: write LVTPC cost is 20.2 cycles (1600 total)
perfctr: driver 2.7.3, cpu type Intel P4 at 2405401 kHz

PERFCTR INIT: vendor 0, family 15, model 2, stepping 7, clock 2395054 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 328 cycles
PERFCTR INIT: rdtsc cost is 76.5 cycles (5224 total)
PERFCTR INIT: rdpmc cost is 145.6 cycles (9648 total)
PERFCTR INIT: rdmsr (counter) cost is 254.1 cycles (16592 total)
PERFCTR INIT: rdmsr (escr) cost is 165.3 cycles (10908 total)
PERFCTR INIT: wrmsr (counter) cost is 780.8 cycles (50300 total)
PERFCTR INIT: wrmsr (escr) cost is 859.6 cycles (55348 total)
PERFCTR INIT: read cr4 cost is 3.6 cycles (564 total)
PERFCTR INIT: write cr4 cost is 252.5 cycles (16492 total)
PERFCTR INIT: rdpmc (fast) cost is 58.8 cycles (4096 total)
PERFCTR INIT: rdmsr (cccr) cost is 166.1 cycles (10960 total)
PERFCTR INIT: wrmsr (cccr) cost is 819.7 cycles (52792 total)
PERFCTR INIT: write LVTPC cost is 33.5 cycles (2472 total)
perfctr: driver 2.7.3, cpu type Intel P4 at 2395054 kHz