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#! rnews 1566 sserve.cc.adfa.oz.au Path: sserve!newshost.anu.edu.au!harbinger.cc.monash.edu.au!simtel!news.sprintlink.net!cs.utexas.edu!math.ohio-state.edu!news.cyberstore.ca!skypoint.com!cyberoptics.com!bpeters!not-for-mail From: peterson@bpeters.cyber.mn.org (Bruce Peterson) Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: IRQ 9 unsafe? Date: 4 Jul 1995 13:54:23 -0500 Organization: Individual Lines: 25 Message-ID: <3tc2ov$3u5@bpeters.cyber.mn.org> References: <gztQkHQ@quack.kfu.com> <3t940q$cf4@anshar.shadow.net> NNTP-Posting-Host: bpeters.uucp In article <3t940q$cf4@anshar.shadow.net>, Don Whiteside <dwhite@anshar.shadow.net> wrote: >Nick Sayer (nsayer@quack.kfu.com) wrote: >: I suspect, however, that the problem >: might simply have been attempting to make use of IRQ 9, which I >: believe has some other use in ISA PCs. Anyone have any words of >: wisdom on this subject? > > IRQ 9 is indeed a cascaded IRQ 2. IRQs 8, 9, 10, 11, 12, 13, 14, and 15 are all cascaded into IRQ 2. IRQ 9 is special only in that on AT class motherboards it is connected to the pin on the expansion bus that IRQ 2 was connected to on pre-AT class motherboards. The thing to watch out for is a conflict where another device is using the same IRQ. Some old graphics adapters used IRQ 2 (on the 8-bit card, which is IRQ 9 on the AT motherboard). Modern VGA adapters often still have a jumper to use IRQ 2 in order to run the (very) old software that made use of it. I haven't heard of any problems using IRQ 9, as long as the video is not also using it. -- Bruce Peterson - peterson@cyberoptics.com