Date: Tue, 12 May 1998 15:33:15 -0700 From: David Greenman <dg@root.com> To: Terry Lambert <tlambert@primenet.com> Cc: steve@visint.co.uk, freebsd-current@FreeBSD.ORG Subject: Re: Intel Etherexpress PRO/100+ PCI Message-ID: <199805122233.PAA28496@implode.root.com> In-Reply-To: Your message of "Tue, 12 May 1998 18:21:13 -0000." <199805121821.LAA23722@usr04.primenet.com>
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>> Terry just doesn't understand how interrupts work on the PCI bus, despite >> providing a nice picture. :-) All of the PCI cards with a single interrupt >> will use INT A - that's just how it works and is the reason for the interrupts >> being cascaded the way they are on the bus. INT A on one slot is not the same >> interrupt on another. > >??? > >Uh, that's what I said. No, you said that you thought the reporting was wrong because one card should report using on INT A while another should report using INT B, etc. >I think it's unlikely that cards in two different slots will have INT a >assigned to them, unless the bus lines are *not* cascaded, which I also >think is unlikely on a modern motherboard. > >Why are both cards reported on INT a? ...and here you say this again. INT A is a PCI bus pin, it is not a specific interrupt. All of the PCI cards that need to interrupt use the "INT A" line, but since that is different for each slot, a different physical interrupt is usually used. A card would use INT B usually only after also using INT A (i.e. it needs two interrupts). Which "INT" line the card uses is a function of how the card is wired and has nothing to do with the BIOS or FreeBSD. So, the "INT" letter is irrelevant. What you should be paying attention to is the irq number that is reported, and you want that to be unique if possible. -DG David Greenman Co-founder/Principal Architect, The FreeBSD Project To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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