APIC

Advanced Programmable Interrupt Controller. Developed by Intel to replace the old PIC standard. Mainly to solve the limited available IRQs problem and to support interrupts on SMP systems.

APIC can still cause many problems (often caused by hardware not conforming to the official APIC standard specification) like hard lockups or devices not working properly. You can then try to turn it off to see if APIC is the problem. To turn APIC on/off add this to the kernel parameters:

apic=off

Either in LILO's lilo.conf or GRUB's menu.lst file (or whatever your bootloader uses).

Or to turn off only local APIC:

lapic=off

Do not confuse APIC with ACPI.