Monk’s Blog

The newer MCP61+ chipsets have busted Interrupt Routing when HPET is turned on. When you enable HPET in the bios, 8254 timer0 stops working/counting!

Solution? Turn OFF hpet and force enable hpet (in linux). It appears to still count even though the BIOS says it’s disabled. Another intresting note, HPET on MCP boards
runs at 25mhz, but I don’t think they are reporting their correct operating frequencies.

Hardware

Phenom:

nothing: 67 cycles
locked add: 80 cycles
cpuid: 116 cycles

Opteron 275:

nothing: 8 cycles
locked add: 6 cycles
cpuid: 61 cycles

Intel Woodcrest:

nothing: 60 cycles
locked add: 72 cycles
cpuid: 264 cycles

Hardware