Return to BSD News archive
Path: sserve!newshost.anu.edu.au!harbinger.cc.monash.edu.au!msuinfo!agate!howland.reston.ans.net!gatech!newsxfer.itd.umich.edu!zip.eecs.umich.edu!yeshua.marcam.com!charnel.ecst.csuchico.edu!psgrain!news.tek.com!news.bv.tek.com!tekgen!troyc From: troyc@tekgen.NoSubdomain.NoDomain (Troy Curtiss;) Newsgroups: comp.os.386bsd.questions Subject: Re: IRQ 2 Re-mapped to 9? Date: 13 Aug 1994 00:13:13 GMT Organization: Tektronix, Inc, Beaverton, OR, USA Lines: 12 Sender: troyc@tekgen (Troy Curtiss;) Distribution: usa Message-ID: <32h36p$csf@tekgen.bv.tek.com> References: <1994Aug12.210012.15677@newsgate.sps.mot.com> NNTP-Posting-Host: localhost.bv.tek.com This is a consequence of PC architecture. In order to get more IRQ space, they decided to cascade two 8259 Interrupt Controller chips. The cascade is from the interrupt output line of the secondary chip to the input IRQ line 2 of the primary chip. This in makes IRQ1 on chip 2 into IRQ2 (or 9) on the primary chip. That's about all I know, as far as using your 3C503 card, I use mine on IRQ 4 or 5, whichever is usually assigned to LPT2 (which most people don't have). Troy Curtiss, HW/SW Engineer Merix Corporation (yet another Tektronix spinoff) troyc@trask.merix.com