Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uunet!convex!eugene!swarren
From: swarren@eugene.uucp (Steve Warren)
Newsgroups: comp.sys.amiga
Subject: Re: Non-Zorro slots in the Amiga 3000
Keywords: 3000 slots
Message-ID: <3751@convex.UUCP>
Date: 7 Dec 89 17:30:37 GMT
References: <5906@ubc-cs.UUCP>
Sender: usenet@convex.UUCP
Reply-To: swarren@convex.COM (Steve Warren)
Distribution: na
Organization: Convex Computer Corporation, Richardson, Tx.
Lines: 39

In article <5906@ubc-cs.UUCP> panon@cheddar.cc.ubc.ca (Paul-Andre Panon) writes:
>
>  Ho, I could be wrong but I don't see how they could fit PC or Nubus slots in
>an A3000 in a way similar to the way it's done on the A2000 and still have
>it fit on a desktop (i.e. have a reasonable footprint). I would expect the
>Zorro III slots in the machine have AT LEAST 24 more pins/lines to support, so
>that 32 data and 32 address lines can be accessible by all peripherals. That
>doesn't include any additional lines Commodore engineers may have decided would
>be useful since the Zorro II specs. were hashed out for the A2000. If they add
>the lines on (at one end or another) a la AT bus, form factor problems develop
>using existing bridgeboard designs.

There is an easy way to design zorro III so that the same space is used
as zorro II, while allowing zorro II to plug into the same connectors:


#I I I I I I I I I I I I I I I I I I I I I I I I I I I#  <-zorro II fingers
#                        # <- ridge to keep zorro II boards from III fingers
#I I I I I I I I I I I I # I I I I I I I I I I I I I I#  <-zorro III fingers
#######################################################  <-connector case

The bottom row, "zorro III fingers" only has the additional data, address,
and control lines that are unique to the zorro III standard, and uses the
same lines as zorro II for the rest of each bus.

Older boards can plug into the connector and only make contact with the
zorro II fingers.

Newer boards have a slice cut out of them so they can seat down into
the ridge, and they have two rows of contacts to connect to both
the zorro II and the zorro III fingers.

This technique is already being used in "blue" land.  Yes, they do
manage to do some things right out there, and I think this is a
good example.

--Steve
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