Re: Strange Problem Amiga 2000

From: Mia Magnusson <mia_at_plea.se>
Date: Sat, 6 Oct 2018 20:52:32 +0200
Message-ID: <20181006205232.00007a66@plea.se>
Den Sat, 6 Oct 2018 19:52:23 +0200 skrev Francesco Messineo
<francesco.messineo@gmail.com>:
> On Sat, Oct 6, 2018 at 7:45 PM Gerrit Heitsch
> <gerrit@laosinh.s.bawue.de> wrote:
> >
> >
> > Well, this version is using an early version of the Zorro bus, the
> > whole logic implemented in PALs and TTLs and not a BUSTER chip as
> > in the later A2000 where AGNUS came in 84pin PLCC instead of 48pin
> > DIP. There are some problems with the bus protocol on the Zorro
> > slots.

Well, the "protocol" itself is mostly just the autoconfig process,
which is super simple to implement (and most likely not a problem). The
problems it might have seems more likely to be of the analogue kind,
i.e. reflections or similar.

That might, or might not, be an issuie in your case.

> > The main difference is that if you use a CPU card with this A2000,
> > you have to remove the 68000 from the mainboard.
> >
> > But then, I am not using a CPU card or any kind of expansion card
> > in it and I either have to use the right CPU (the ST 68000) when
> > using KS 1.3 or just use KS 1.2 with any 68000 to have no problems
> > at all.
> 
> I don't know what type of chip "hosts" the Kickstart (I'm not so
> expert on Amigas), but did you try to copy the KS 1.3 on different
> EPROMs?

One problem is that almost no one who's not an "Amiga kickstart burner"
has those EPROM's in their good-to-have junk box. They are 16-bit and
therefore much rarer.

> Sounds like some weird decoupling/logic-threshold/rail-bouncing
> problem. I would have a good look at the CPU bus with a logic
> analyzer.

Agreed, but maybe an oscilloscope would be better, as it's not unlikely
that the issue needs a faster tool than most logic analyzers.

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Received on 2018-10-06 21:02:13

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