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what does apic do?

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Jul 14, 2002
What is APIC? APIC is a distributed set of devices that make up an interrupt controller. In current implementations, each part of a system is connected by an APIC bus. One part of the system, the "local APIC," delivers interrupts to a specific processor; for example, a machine with three processors must have three local APICs. Intel has been building local APICs into their processors since the Pentium P54c in 1994. Computers built with genuine Intel processors already contain part of the APIC system.

The other important part of the system is the I/O APIC. There can be as many as eight I/O APICs on a system; they collect interrupt signals from I/O devices and send messages to the local APICs when those devices need to interrupt. Each I/O APIC has an arbitrary number of interrupt inputs (or IRQs). Intel's past and current I/O APICs typically have 24 inputs--others can have as many as 64. And some machines have several I/O APICs, each with a number of inputs, amounting to hundreds of IRQs in the machine that are available for device interrupts.

However, without an I/O APIC in the system, the local APICs are useless. In such a situation, Windows 2000 has to revert to using the 8259 PIC.

well... thats like wow !

so can anyone tell me what that means or like yea im still clueless about it cant understand that

*edit ok i guess what im trying to get at is should i turn apic on or off on my mobo, and maybe a brief description of what it does**

thanks again