[data from a 2.2GHz Pentium 4]

PERFCTR INIT: vendor 0, family 15, model 2, stepping 9, clock 2192380 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 228 cycles
PERFCTR INIT: rdtsc cost is 78.1 cycles (5228 total)
PERFCTR INIT: rdpmc cost is 147.1 cycles (9644 total)
PERFCTR INIT: rdmsr (counter) cost is 255.6 cycles (16592 total)
PERFCTR INIT: rdmsr (escr) cost is 166.6 cycles (10896 total)
PERFCTR INIT: wrmsr (counter) cost is 803.7 cycles (51668 total)
PERFCTR INIT: wrmsr (escr) cost is 890.8 cycles (57240 total)
PERFCTR INIT: read cr4 cost is 5.1 cycles (556 total)
PERFCTR INIT: write cr4 cost is 255.7 cycles (16596 total)
PERFCTR INIT: rdpmc (fast) cost is 60.3 cycles (4092 total)
PERFCTR INIT: rdmsr (cccr) cost is 167.6 cycles (10956 total)
PERFCTR INIT: wrmsr (cccr) cost is 838.8 cycles (53916 total)
perfctr: driver 2.7.3, cpu type Intel P4 at 2192380 kHz