[data from a 2.8GHz HT P4]

perfctr/x86.c: hyper-threaded P4s detected: restricting access for CPUs 1
PERFCTR INIT: vendor 0, family 15, model 3, stepping 3, clock 2798934 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 322 cycles
PERFCTR INIT: rdtsc cost is 121.1 cycles (8078 total)
PERFCTR INIT: rdpmc cost is 225.7 cycles (14770 total)
PERFCTR INIT: rdmsr (counter) cost is 362.5 cycles (23527 total)
PERFCTR INIT: rdmsr (escr) cost is 384.1 cycles (24906 total)
PERFCTR INIT: wrmsr (counter) cost is 983.5 cycles (63266 total)
PERFCTR INIT: wrmsr (escr) cost is 997.3 cycles (64155 total)
PERFCTR INIT: read cr4 cost is 24.3 cycles (1883 total)
PERFCTR INIT: write cr4 cost is 394.1 cycles (25550 total)
PERFCTR INIT: rdpmc (fast) cost is 92.0 cycles (6216 total)
PERFCTR INIT: rdmsr (cccr) cost is 393.3 cycles (25494 total)
PERFCTR INIT: wrmsr (cccr) cost is 951.2 cycles (61201 total)
PERFCTR INIT: write LVTPC cost is 17.5 cycles (1442 total)
perfctr: driver 2.7.3, cpu type Intel P4 at 2798934 kHz

PERFCTR INIT: vendor 0, family 15, model 2, stepping 9, clock 2781965 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 520 cycles
PERFCTR INIT: rdtsc cost is 78.5 cycles (5544 total)
PERFCTR INIT: rdpmc cost is 147.1 cycles (9936 total)
PERFCTR INIT: rdmsr (counter) cost is 255.8 cycles (16892 total)
PERFCTR INIT: rdmsr (escr) cost is 166.9 cycles (11204 total)
PERFCTR INIT: wrmsr (counter) cost is 802.2 cycles (51864 total)
PERFCTR INIT: wrmsr (escr) cost is 889.1 cycles (57428 total)
PERFCTR INIT: read cr4 cost is 5.1 cycles (852 total)
PERFCTR INIT: write cr4 cost is 254.6 cycles (16816 total)
PERFCTR INIT: rdpmc (fast) cost is 60.9 cycles (4420 total)
PERFCTR INIT: rdmsr (cccr) cost is 167.7 cycles (11256 total)
PERFCTR INIT: wrmsr (cccr) cost is 837.2 cycles (54104 total)
PERFCTR INIT: write LVTPC cost is 39.6 cycles (3060 total)
PERFCTR INIT: sync_core cost is 264.1 cycles (17428 total)
perfctr: driver 2.7.5, cpu type Intel P4 at 2781965 kHz

[data from a 2.8GHz P4 w/o HT]
PERFCTR INIT: vendor 0, family 15, model 2, stepping 7, clock 2806891 kHz
PERFCTR INIT: NITER == 64
PERFCTR INIT: loop overhead is 516 cycles
PERFCTR INIT: rdtsc cost is 78.9 cycles (5568 total)
PERFCTR INIT: rdpmc cost is 146.5 cycles (9896 total)
PERFCTR INIT: rdmsr (counter) cost is 255.6 cycles (16880 total)
PERFCTR INIT: rdmsr (escr) cost is 166.7 cycles (11188 total)
PERFCTR INIT: wrmsr (counter) cost is 793.9 cycles (51328 total)
PERFCTR INIT: wrmsr (escr) cost is 873.0 cycles (56388 total)
PERFCTR INIT: read cr4 cost is 5.2 cycles (852 total)
PERFCTR INIT: write cr4 cost is 254.0 cycles (16776 total)
PERFCTR INIT: rdpmc (fast) cost is 60.8 cycles (4412 total)
PERFCTR INIT: rdmsr (cccr) cost is 167.6 cycles (11248 total)
PERFCTR INIT: wrmsr (cccr) cost is 833.1 cycles (53836 total)
PERFCTR INIT: sync_core cost is 264.0 cycles (17412 total)
perfctr: driver 2.7.15, cpu type Intel P4 at 2806891 kHz