[data from a 1.8 GHz Pentium 4 (Willamette)]

PERFCTR INIT: vendor 0, family 15, model 1, stepping 3, clock 1794572 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 512 cycles
PERFCTR INIT: rdtsc cost is 78.1 cycles (5512 total)
PERFCTR INIT: rdpmc cost is 144.3 cycles (9752 total)
PERFCTR INIT: rdmsr (counter) cost is 247.5 cycles (16356 total)
PERFCTR INIT: rdmsr (escr) cost is 166.6 cycles (11176 total)
PERFCTR INIT: wrmsr (counter) cost is 827.3 cycles (53460 total)
PERFCTR INIT: wrmsr (escr) cost is 886.0 cycles (57220 total)
PERFCTR INIT: read cr4 cost is 4.9 cycles (828 total)
PERFCTR INIT: write cr4 cost is 244.9 cycles (16188 total)
PERFCTR INIT: rdpmc (fast) cost is 60.6 cycles (4396 total)
PERFCTR INIT: rdmsr (cccr) cost is 167.5 cycles (11236 total)
PERFCTR INIT: wrmsr (cccr) cost is 846.0 cycles (54660 total)
PERFCTR INIT: sync core cost is 257.5 cycles (16996 total)
perfctr: driver 2.7.6, cpu type Intel P4 at 1794572 kHz