Re: 2.3.20 will not boot (PCI problem)

Alan Cox (alan@lxorguk.ukuu.org.uk)
Mon, 11 Oct 1999 10:47:50 +0100 (BST)


> Unfortunately, we use the interrupt routing table not only for fixing bad
> IRQ's, but also for detecting peer host bridges. We could disable this BIOS
> call by default, make it an option and hope that all new multi-bus machines
> will provide the $PIR table and handle the rest by chipset-specific kludge.

You have to handle the PIIX4 by kludge. The $PIR table is set up on the
basis you are windows and will do this. The BIOS call for getting the table
is known to fail on a whole pile of BIOSen too. Enough that MS don't use
it by default.

On a PC the PIIX4 is provided with a PIIX2 table. Windows loads up a driver
of its own to handle this when it sees the PIIX2 routing table on a PIIX4.

It's also worth noting that Microsoft consider it sufficiently unreliable that
they don't attempt to use any IRQ steering features unless they have to.

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