[data from a 750MHz Duron]

PERFCTR INIT: vendor 2, family 6, model 3 
PERFCTR INIT: NITER == 64 
PERFCTR INIT: loop overhead is 88 cycles 
PERFCTR INIT: rdtsc cost is 11.2 cycles (805 total) 
PERFCTR INIT: rdpmc cost is 12.9 cycles (918 total) 
PERFCTR INIT: rdmsr (counter) cost is 51.7 cycles (3400 total) 
PERFCTR INIT: rdmsr (evntsel) cost is 52.7 cycles (3465 total) 
PERFCTR INIT: wrmsr (counter) cost is 81.6 cycles (5314 total) 
PERFCTR INIT: wrmsr (evntsel) cost is 231.6 cycles (14913 total) 
PERFCTR INIT: read %cr4 cost is 4.7 cycles (390 total) 
PERFCTR INIT: write %cr4 cost is 62.9 cycles (4119 total) 
perfctr: driver 2.0-pre3, cpu type AMD K7 at 749671 kHz