Date: Thu, 9 Nov 2000 10:03:28 -0800
From: Michael Perry
Sean Akers@ROMAX 09/11/2000 17:12
AFAIK, the PCI hardware standard requires that all PCI cards MUST be able to share IRQs. I've never seen Linux share PCI IRQs though. Windows 2000 makes use of this requirement to a fault in fact. In every Windows 2000 I've installed, it puts just about every PCI device at the same IRQ whether you want it to or not. On my W2K system at home, the video, network, sound and Promise Ultra/66 cards all share the same IRQ (and there's no way of changing this either which gets right up my nose). I'm sure it would be more efficient to spread these devices over all the available IRQs and only double up when you've run out after all, the OS must be doing some sort of polling when it gets an interrupt on a shared IRQ to find out which device needs servicing.
My SuSE 6.4 Linux server has 2 PCI network cards, a PCI SCSI card and a PCI video card. All are automatically put on different IRQs. Perhaps someone can tell us about IRQ sharing under Linux in more details but I expect it does it the sensible way by spreading things out as much as possible.
Sean.
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I could not get IRQ sharing to work on several boxes under Linux. I had a pci ethernet card sitting next to a sblive card on the pci bus. They wanted to share irqs and play nice and in the bios they did play nice. Linux gave the irq to the network card and would not share. I finally pulled the sound card and moved it down one slot on the pci bus and it worked quite well. I don't have a great answer or even a modest success story. I could never get the irq sharing working on pci cards whatsoever. -- Michael Perry mperry@tsoft.com ------------------