APIC: Difference between revisions
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IO-APIC version 0x20 has 3 registers. |
The Window Register has bits 8 thru 31 reserved, so ensure that 1's are never written to them |
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The IO APIC uses two registers for most of its operation - an address register at IOAPICBASE+0 and a data register at
IOAPICBASE+0x10. All accesses must be done on dword boundaries. The address register uses the bottom 8 bits for register select. Here is some example code that illustrates this:
<source lang="c">
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{
volatile dword * ioapic = (volatile dword*)ioapicaddr;
ioapic[0] = (reg & 0xff);
return ioapic[4];
}
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{
volatile dword * ioapic = (volatile dword*)ioapicaddr;
ioapic[0] = (reg & 0xff);
ioapic[4] = value;
}
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