IRQS on 6 Slot Macs

Mich Lanners mlan at
Tue Nov 4 08:30:11 EST 2003

On   3 Nov, this message from Geert Uytterhoeven echoed through
>> > I don't know what's up with the DRM not liking your interrupt. I
>> > can answer for the sharing of USB, symbios and firewire interrupts:
>> > all 3 slots share one interrupt because of bad motherboard design
>> > :) Basicallly, what they did when designing that machine was to use
>> > a standard powersurge design with 3 slots and replace one of them
>> > with a PCI<->PCI bridge. Since they didn't "know" how to get more
>> > interrupt lines out of Grand Central, they just also stuffed all
>> > interrupt lines together for those 4 slots (I'm pretty sure GC do
> Tsss... They could at least have `swizzled' the lines...

Sure, but it's indeed totally not understandable why they didn't use the
other lines on GrandCentral, since the 9500/9600 design includes six PCI
slots with each a dedicated IRQ line. Weird...


Michel Lanners                 |  " Read Philosophy.  Study Art.
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