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Seattle, WA, USA

Posted Fri Sep 18, 2020 1:10 pm

A while back I got a very strange and unusual 3rd party device with an Amiga 500 haul I'd purchased through Reddit.

The haul included a boxed, minty very early A500, an A590 and a really large pizza box sized metallic thing with a very large, heavy and kind of scary looking PSU.

I've kept the A500, but ultimately decided to sell the hard drive and strange pizza box thing.

It took my local friend Christian, who is a walking Book of Amiga Hardware, to identify it. It's called the Pacific Peripherals SubSystem 500.
Screen Shot 2020-09-16 at 4.53.35 PM.png

In case that print is tough to read, here are the details.
  • 2× Zorro II slots with DMA support
  • 1× 3.5" drive bay for an optional 2nd floppy drive
  • external power supply
  • connects to the side expansion port
  • fits under the Amiga
It's a painted metal case, so it'll never turn yellow.

Image from iOS (1).jpg
Naked and exposed.

Check out the wacky power connector. Is that for a C64? Nope.


Mine is the "premium" version with the extra DF1: 3.5" floppy drive that originally retailed for a whopping $399 back in 1987/88 (approximately $875 in 2020 dollars).

in theory you could eliminate a large external hard drive (like the A590, or GVP Impact HD8+) and use a SCSI Zorro II card to have an internal hard drive and reclaim some of that desk space. It had metal plates on the back for mounting additional ports, too, in case you wanted to use even more devices.

But, the side expansion connector also had a hard pass-through so you could use your pre-existing external HDD if you wanted to, which is just nuts. You'd probably have to put a book under it, though, and maybe even decide to raise your desk chair a couple of inches along the way. Hah!

In any case, this is the only one of these I've ever seen. But I was too chicken to ever try and hook it all up. I've decided that's a fun project someone else should enjoy. The PSU weighs a respectable 13.5 pounds!

I did want to capture several photos of it, first, before I said good-bye.

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Lexington VA

Posted Sat Sep 19, 2020 2:14 pm

Ha! I was about to say, I just saw this thing on ebay... and yeah lol.

Id be curious to know how they got two zorro ii slots working with dma on the 500, I didnt think it had the chips for bus for it to work correctly.

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Posted Sun Sep 20, 2020 12:39 am

Same here. I am sure they don’t support DMA. Maybe they tried to bury something like ‚one of the cards may be DMA and two cards in total are possible‘ in the advertising speech.

Great idea, to be fair.

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Posted Sun Sep 20, 2020 9:30 pm

It is possible to build an expansion board that supports Zorro 2 DMA. That’s exactly what the A2000A is - an A1000 with an Zorro 2 bus board added on the same PCB.
You can have multiple external DMA devices if the bus board adds the necessary arbitration logic (this is described in the A500/A2000 Technical Reference Manual)

What won’t work is an external accelerator and an external DMA device (well, it will work if the accelerator is closer to the computer and if they are doing some tricks - see GVP A530 which is an external accelerator + SCSI DMA host adapter). For that to work in a generalized way, you’d need the A2000B coprocessor interface which the A500/A1000 do not have.

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Posted Sun Sep 20, 2020 11:37 pm

Sorry if I wasn’t precise. I am aware that it’s possible. I don’t think they managed to do this with this board.

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Seattle, WA, USA

Posted Mon Sep 21, 2020 8:46 pm

For those with engineering expertise that may find this interesting.

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Posted Tue Sep 22, 2020 10:21 am

Most of that logic (the NAND 7438 and the Flip Flop 7474) are used to generate the ID stream bit pattern for the floppy drive. it is the same logic that you see in an A1010, A1011 and other external Amiga floppy drives.

No logic for buffering the bus nor for handling multiple DMA cards.

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