From: Maciej W. Rozycki (
Date: Tue Sep 17 2002 - 06:22:15 EST

On Mon, 16 Sep 2002, James Cleverdon wrote:

> For APICs, when two interrupts are present when interrupts are enabled, the
> one with the highest interrupt vector number will be taken first. Vectors
> are statically assigned to the PCI slots, starting at 0x40 or 0x41. So, the

 Vectors start from 0x31. That's what IRQ 0 gets. The interval is 8, so
the following vectors are 0x39, 0x41, and so on.

> last PCI interrupt source in the MPS table will be the highest priority.

 Not necessarily -- after reaching the reserved range, i.e. 0xef, the
allocation wraps around to the previous base plus one. So for the second
pass vectors start from 0x32, for the third -- 0x33, etc.

+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+        e-mail:, PGP key available        +

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