Path: utzoo!utgpu!news-server.csri.toronto.edu!torsqnt!lethe!yunexus!rreiner From: rreiner@yunexus.YorkU.CA (Richard Reiner) Newsgroups: comp.sys.ibm.pc.hardware Subject: Re: IRQ 2 on AT-class machines Message-ID: <22640@yunexus.YorkU.CA> Date: 4 May 91 13:40:18 GMT Article-I.D.: yunexus.22640 References: <22603@yunexus.YorkU.CA> <160@thor.sdrc.com> <3WC+R0F@jwt.UUCP> Organization: York U. Computing Services Lines: 18 li@mrcnext.cso.uiuc.edu (hans li) writes: >On AT class machines irq 2 is used for daisy chaining disk drives. What is your source for this information? What drive controllers do you claim do this? I've never seen any. Besides, you must mean IRQ9: see below. >IRQ 9 is supposed to be used for networks and other cards. Although true, this contradicts the above, since IRQ2 does not appear on the AT bus, its place having been taken by IRQ9. The physical IRQ2 on PIC1 is used as the cascade from PIC2, and for nothing else. Talk about "what IRQ2 is used for on the AT bus" is really about "the IRQ line that takes the place on the bus of IRQ2," namely IRQ9. So these two things, the line takng the place of IRQ2, and IRQ9, cannot have dfferent uses, since they are one and the same, i.e. IRQ9.