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Newsgroups: comp.unix.bsd Path: sserve!manuel.anu.edu.au!munnari.oz.au!spool.mu.edu!uwm.edu!zaphod.mps.ohio-state.edu!saimiri.primate.wisc.edu!sdd.hp.com!wupost!darwin.sura.net!jvnc.net!yale.edu!ira.uka.de!math.fu-berlin.de!mailgzrz.TU-Berlin.DE!news.netmbx.de!netmbx!gerhard From: gerhard@netmbx.netmbx.de (Gerhard Hoffmann) Subject: Re: [386BSD] 16550 Not Resetting. Organization: netmbx, Berlin, Germany Date: Wed, 2 Dec 1992 01:39:24 GMT Message-ID: <SJF9YPB@netmbx.netmbx.de> References: <1992Nov28.115716.8219@runx.oz.au> <CGD.92Nov28202543@eden.CS.Berkeley.EDU> <1992Nov30.131213.18948@runx.oz.au> Lines: 25 Bruce Evans (bde@runx.oz.au) wrote: >Blame the hardware. After the software has put the h/w in a weird state, >it is often too difficult, and sometimes impossible, to recover without a >full h/w reset. Yet the h/w doesn't provide any (standard?) way to force >a h/w reset from s/w. 386BSD shuts down by causing a triple fault. My >understanding is that this doesn't reset the h/w, it just shuts down the >cpu, then on most systems the motherboard h/w detects the shutdown and >causes some sort of reset. I wonder why the reset isn't full? Perhaps >so that it can be used to switch 286's out of protected mode. The triple fault doesn't reset anything but the cpu. It is a bug ( too difficult to handle) declared a feature and has been used by DOS ex- tenders to leave protected mode for a moment in order to do a syscall. Not much of a system reset. If you want to do a REAL RESET, ask the keyboard controller to do it: outb ( 0x64, 0xf0 ); a triple fault --- aaarggh! -- # Gerhard Hoffmann # phone: +49 30 782 02 33 # # Gleditschstr. 79 # fax: +49 30 782 02 63 # # D1000-62 Berlin, Germany # on the air: dk4xp # # gerhard@netmbx # in the air: D-1441, D-KICK #