[data from a 2.8 GHz Pentium 4 Xeon (Northwood)]

PERFCTR INIT: vendor 0, family 15, model 2, stepping 9, clock 2786536 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 556 cycles
PERFCTR INIT: rdtsc cost is 77.7 cycles (5532 total)
PERFCTR INIT: rdpmc cost is 146.0 cycles (9900 total)
PERFCTR INIT: rdmsr (counter) cost is 254.8 cycles (16868 total)
PERFCTR INIT: rdmsr (escr) cost is 166.0 cycles (11180 total)
PERFCTR INIT: wrmsr (counter) cost is 1016.5 cycles (65616 total)
PERFCTR INIT: wrmsr (escr) cost is 913.8 cycles (59044 total)
PERFCTR INIT: read cr4 cost is 4.4 cycles (840 total)
PERFCTR INIT: write cr4 cost is 253.9 cycles (16808 total)
PERFCTR INIT: rdpmc (fast) cost is 60.1 cycles (4408 total)
PERFCTR INIT: rdmsr (cccr) cost is 166.8 cycles (11232 total)
PERFCTR INIT: wrmsr (cccr) cost is 838.6 cycles (54232 total)
PERFCTR INIT: write LVTPC cost is 25.4 cycles (2184 total)
PERFCTR INIT: sync_core cost is 263.6 cycles (17428 total)
perfctr: driver 2.7.6, cpu type Intel P4 at 2786536 kHz

PERFCTR INIT: vendor 0, family 15, model 2, stepping 7, clock 2799309 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 264 cycles
PERFCTR INIT: rdtsc cost is 82.1 cycles (5520 total)
PERFCTR INIT: rdpmc cost is 151.1 cycles (9940 total)
PERFCTR INIT: rdmsr (counter) cost is 255.0 cycles (16584 total)
PERFCTR INIT: rdmsr (escr) cost is 166.2 cycles (10904 total)
PERFCTR INIT: wrmsr (counter) cost is 793.0 cycles (51020 total)
PERFCTR INIT: wrmsr (escr) cost is 872.7 cycles (56120 total)
PERFCTR INIT: read cr4 cost is 5.0 cycles (584 total)
PERFCTR INIT: write cr4 cost is 253.6 cycles (16500 total)
PERFCTR INIT: rdpmc (fast) cost is 61.2 cycles (4184 total)
PERFCTR INIT: rdmsr (cccr) cost is 167.0 cycles (10952 total)
PERFCTR INIT: wrmsr (cccr) cost is 832.8 cycles (53564 total)
perfctr: driver 2.5.5, cpu type Intel Pentium 4 Model 2 at 2799309 kHz