From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: IRQS on 6 Slot Macs From: Benjamin Herrenschmidt To: Robert E Brose II Cc: linuxppc-dev list In-Reply-To: <20031103033529.24416.qmail@kunk.qbjnet.com> References: <20031103033529.24416.qmail@kunk.qbjnet.com> Content-Type: text/plain Message-Id: <1067842481.17970.8.camel@gaston> Mime-Version: 1.0 Date: Mon, 03 Nov 2003 17:54:41 +1100 Sender: owner-linuxppc-dev@lists.linuxppc.org List-Id: On Mon, 2003-11-03 at 14:35, Robert E Brose II wrote: > A couple of things right off, the rage128 appears to be the only thing on > irq 23 however 23 doesn't show up in /proc/interrupts meaning, I suppose, > that it's not using the interrupt. So why does the drm complain? > > How come everything from slots 3-6 says it's on the same interrupt (25)? 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 have spare lines they could have used, but that would have meant updating Open Firmware to understand the layout, I doubt the people who designed that machine wanted to dive into that). Ben. ** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/