Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!rutgers!cbmvax!daveh From: daveh@cbmvax.commodore.com (Dave Haynie) Newsgroups: comp.sys.amiga.hardware Subject: Re: 68020 dilemma Message-ID: <9779@cbmvax.commodore.com> Date: 22 Feb 90 08:33:30 GMT References: Reply-To: daveh@cbmvax.cbm.commodore.com (Dave Haynie) Organization: Commodore, West Chester, PA Lines: 33 In article ms0p+@andrew.cmu.edu (Michael Gordon Shapiro) writes: >The computer had other ideas, however, and simply wouldn't reboot. >This was very distrubing. I tried booting in 68000 mode, and found that >the machine GURUs... (810000009.41F9000F) but then works. A GURU when switching from 68020 to 68000 mode, without powerdown, is essentially normal. Exec won't re-check CPU type unless it actually rebuilds a significant portion of itself (which always happens, of course, on a cold boot). So the system fires up with the wrong idea of what CPU's in charge, and crashes as soon as that matters. >ONCE -- and I don't know quite how -- I managed to get it to boot in >68020 mode. Since then I've been having no luck, even after turning >off power, etc. It's hard to guess what's wrong; this certainly isn't anything like a known failure mode. The first thing I would do is open up the machine and re-seat the 68020 card. If that doesn't help things, you can at least get an idea of what could be wrong by running the monitor's memory test. Go to the mode list and type an upper-case "M". Once in the monitor, type "T 200000 400000". This will indicate a memory failure if it finds one. Ideally, the re-seating is all that's required, and that's sure enough easier than trucking the whole thing down to the service center. I would put the chance of a poorly seated card eventually working its way loose at about 100%, while there chance of a part going bad isn't non-existant, but it's not common. -- Dave Haynie Commodore-Amiga (Systems Engineering) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy Too much of everything is just enough