>>: : Zorro I and II are very similar, the Amiga 500 and 1000 have Zorro I, the
>>: : 2000 has zorro II.
>>: The A500 has a Zorro II slot.
>> You're doing this delibrately ain't ya?
>> No it doesn't! Look at my previous post. :P :P :P
> I can't find where I stashed it now, but I had a posting from Dave
>Haynie stating that there never was such a thing as an Amiga with a Zorro I
That would be correct! You win the cupie doll!
Basically, back in the A1000 days, the expansion bus design wasn't
done, and there was no practical way to put slots in. So they shipped
the A1000 with The Expansion Edge. This contains most of the Zorro bus
signals, but also what you need to add on extra CPUs, like the A2000
coprocessor slot, which is also resembles.
The expansion specifications came out, and they included a physical
form factor for the first card, which came to be known as "Zorro I".
This was a rectangular card, with connectors along the long edge and a
panel with screws, so it could be installed from the outside of a box.
More like VME bus's card idea than the PC-AT bus.
The next year, there was a project going on, at the small C=
engineering branch in Germany, to make an A1000 follow-up, but one
more like a PC (since, of course, the Germans did all the Commodore
PCs at the time). The folks in charge there wanted the option of using
PC cards, and this "bridge card" idea, to make it easy to have PClone
stuff in the box. This became the A2000, and the PC-AT form-factor of
the Amiga bus became known at Zorro II.
With a few exceptions that rarely made a practical difference, other
than the card didn't mechanically fit. If you took a Zorro I card and
put it in a Zorro II machine, it would proibably work. But it wouldn't
fit if you had the case on, and all the connectors would be pointing
at the ceiling.
Zorro III was something completely different, that just happened to
support Zorro II as a subset, when called for. I did just about all
the Zorro III work at Commodore.
Quote:>The A1000 and A500 have an 86-pin expansion port, which happens to be
>very similar to a single Zorro II slot.
Like I said before, it's actually more like the CPU slot on an A2000.
The original A2000 had an "MMU Slot"; the German group had some idea
of adding an external MMU to the machine, and so they brought out the
68000 bus and a few other signals, mostly from the A1000 edge, to this
MMU slot (it was even an 86-pin slot).
When I got the A2000 "cost reduction" project at Commodore West
Chester, it was pretty clear this idea was silly. But the idea of an
upgrade slot for CPUs rocked. Since I was designing a gate array to
take do the work of several PAL devices and buffers in the original
A2000, it was fairly easy to define new protocols, using most of the
same signals, that made the CPU slot a reality.
I guess it worked. Most computers last about a year or two. The A2000
has been going fairly strong for ten years -- even when it was out of
production, folks were bring out '040 and '060 cards for it, at the
same time, maybe even before they did cards for the A3000/A4000.
Dave Haynie V.P. Hardware Engineering PIOS Computer