Xref: utzoo comp.sys.amiga.programmer:1771 comp.sys.amiga.hardware:7554 Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!unix.cis.pitt.edu!dsinc!bagate!cbmvax!daveh From: daveh@cbmvax.commodore.com (Dave Haynie) Newsgroups: comp.sys.amiga.programmer,comp.sys.amiga.hardware Subject: Re: Is OS supposed to zero the TOD clock registers intermittently? Keywords: Intuition TOD clock bugs race condition Message-ID: <20099@cbmvax.commodore.com> Date: 25 Mar 91 20:09:31 GMT References: <1991Mar21.175806.23729@daffy.cs.wisc.edu> <20076@cbmvax.commodore.com> <1991Mar24.204244.6123@daffy.cs.wisc.edu> Reply-To: daveh@cbmvax.commodore.com (Dave Haynie) Organization: Commodore, West Chester, PA Lines: 83 In article <1991Mar24.204244.6123@daffy.cs.wisc.edu> pochron@cat52.cs.wisc.edu (David Pochron) writes: >And what is stranger is this: >c) How the heck is it possible for the blitter to be banging on memory way > up at $BFE001 anyway? It should be impossible, yet it happens! It is totally impossible. The CPU can point over to the chip bus, but the chip bus can't point toward the CPU bus, the lines just plain don't point that way. I'm not disputing your claim that it looks like this, just that that isn't what's really happening. >d) Again, none of this happens when the A2630 card is disabled. Do you have a way to try another A2630 card... >Which leads me to believe the problem is: >1) The Agnus chip (original, 512K fat lady) is flaky. Possible, but not likely. There's isn't a whole lot Agnus could do to mess with the CIA chips, and still work at all. You'd basically have to have inputs magically turned around as outputs for that to happen. More likely a problem with the Gary chip, is anything. I doubt either is at fault. >2) The A2630 68030 card is flaky. All of this started when I got the card > last year. I wish this were not the case, as it could be very expensive > to track down the extact problem and get it fixed. I'd much rather just > replace an Agnus chip (with a nice 1meg one, too!) Well, the A2630 card is a better target than Agnus. If it were, for example, to get some of the CIA interface signals confused, you might have this kind of problem. I have only known of one A2630 failure personally, and that was one of the TTL parts responsible for preconfiguration setup. Most of the A2630 CIA interface is contained in a pair of PAL chips. Of course, the A2630 does depend on lots of signals from the motherboard, so any real good motherboard mess up would confuse the A2630's operation. While the A2630's CIA timing might differ ever so slightly from a real 68000's, they're both correct by the 68000 spec. If you partially zapped both 8520s, you might just be in that range. 8520s do die in interesting ways. >My motherboard is still only rev. 4.2, but I don't know if it and the A2630 >card are having a problem. Shouldn't be any problem. Most of the boards around here, including the system I'm typing this on (A2000 w/A2630) were around that vintage when I was developing the A2630. >One thing I did notice though, is that the resistor between and just above the >two 8520's is burnt brown and bubbly. It looks like a 47-something ohm >resistor. (I can rember the exact R-number on the PC board.) >I will probably replace it today. Sounds like R310, which is a 47 ohm 1/2 watt resistor. That's the one between the "+5 USER" supply and the +5 on the parallel port. How the heck did you zap that one? Even at a dead short to ground it shouldn't burn up like that. Once it's replaced, check to see that you still have +5 on pin 14 of the parallel port. If that's gone, you could be having all kind of problems (I doubt it is, or you'd lose your mouse too. Whatever did that might have had an adverse effect on the rest of the system, especially the CIA which drives the parallel port. Which is, incidently, the one with the TOD clock in it. Well, actually I guess both do talk to the parallel port -- U300 drives the parallel line and receives the STROBE* handshake, while U301 takes care of the Paper out, busy, select, and acknowledge lines. >I also tried reseating the Agnus chip - didn't make any difference. > >>-- >>Randell Jesup, Keeper of AmigaDos, Commodore Engineering. >>{uunet|rutgers}!cbmvax!jesup, jesup@cbmvax.commodore.com BIX: rjesup > > >-- > > -- David M. Pochron | > | Canada: One of the world's greatest mysteries.. >pochron@garfield.cs.wisc.edu | -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy "That's me in the corner, that's me in the spotlight" -R.E.M.