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-   -   Zorro 2 and A500 (http://eab.abime.net/showthread.php?t=93347)

Nosferax 11 July 2018 16:39

Zorro 2 and A500

I've read that the side expansion port on the A500 is in fact a Zorro 2 slot with an edge connector instead of a slot. If I take two A2000 Zorro 2 slot socket and use them as a gender changer, can I use A2000 Zorro 2 card like the Buddah on the A500?

Amiga4000 11 July 2018 16:55

You are correct in your thought process however, you might have autoconfig & timing issues with only using a couple of sockets. Rob Cranley, AKA Rob the Nerd (http://www.robthenerd.com), manufactured a brilliant Z2 adapter for the A500 "the Z500" and you may still be able to obtain one from him. I have one (one of my Amiga prize possessions) and it's awesome for using/testing A2K boards on the A500. I use my Buddha & IDE2Z2 boards all the time with it. :) See discussion thread here......


Maybe give him a PM shout......

Daedalus 11 July 2018 17:10

Cheers :) Yeah, 95% of the signals are the same, and there have been designs for Zorro board adaptors floating around for decades, as well as several products released over the years that do the job. There was even an article in one of the Amiga Format issues that showed how to make a DIY adaptor out of old PC ISA sockets and a couple of parts.

Most signals are simply 1:1 with the A500's port, but there are a few signals you need to be wary of:

First, the negative power rails: the A500 doesn't supply -5V at all, and supplies -12V on the pin number Zorro designates for -5V. You can probably get away with leaving the -5V off altogether and redirecting the -12V to the correct pin since I'm not sure if many Zorro cards even use -5V. I guess some old audio or video cards might.

Second, Autoconfig needs to be looked at if you're going to use more than one device, e.g. an ACA500 or A570. It can simply be pulled up with a resistor if you're only going to use one or two devices. Adding more devices is possible in theory, but would be better handled by adding some simple logic.

Third, there's a clock signal that the A500 doesn't provide, which is a 7MHz signal that's out of phase with the main 7MHz clock. This can be reconstructed with a small logic IC from two other signals available on the A500. Again, I don't know how many Zorro cards use this, but since almost all designs (including the very rudimentary Amiga Format one) appear to do this, it's probably a safe bet that many cards do need it.

There are other signals that can be tied low or high, and the majority of cards will be happy with that.

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