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Newsgroups: comp.os.386bsd.questions Path: sserve!newshost.anu.edu.au!munnari.oz.au!metro!ipso!runxtsa!bde From: bde@runx.oz.au (Bruce Evans) Subject: Interrupt numbers (was patch support for Chris' com drivers ?) Message-ID: <1993Apr15.042413.5572@runx.oz.au> Organization: RUNX Un*x Timeshare. Sydney, Australia. References: <C5D4sw.B3B@constellation.ecn.uoknor.edu> <1qdio2$mjf@walt.ee.pdx.edu> Date: Thu, 15 Apr 93 04:24:13 GMT Lines: 27 In article <1qdio2$mjf@walt.ee.pdx.edu> rgrimes@acacia (Rodney W. Grimes) writes: >ngorelic@speclab.cr.usgs.gov.cr.usgs.gov (Noel S. Gorelick) writes: >: IRQ 13: npx (what the heck is this?) > >That is the interrupt for the FPU chip, if you do not have an FPU it is used >by the math emulation software. If you do not have an FPU, then nothing uses it (math emulation uses exception 7 (which has nothing to do with any IRQ)). Almost all 386 and 486 systems support FPU's and have hardware to drive IRQ13. I don't know exactly what happens when no FPU is plugged in. The h/w might still drive IRQ13, making it unusable for other devices. >First, 2==9, they are one and the same. Second, 7 is reserved for lpt. 7 has another special purpose (catching spurious interrupts). Otherwise there are no problems using it for a device other than a printer even when a printer port is connected, at least if the driver for the other device knows about the printer and disconnects the printer interrupt. >Third, 8 is reserved for the Real Time clock. 9==2 and is used for lots 8 is connected to the Real Time Clock but the interrupt is usually disabled. The interrupt should be used for better profiling and/or system accounting. -- Bruce Evans bde@runx.oz.au