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Zorro II Cards On The Amiga 500

The next build for my Amiga 500 was a Zorro II Card Slot Adapter. This unit uses the expansion slot on the left-hand side of the Amiga (just like the external IDE adapter) and provides a vertical slot to plug your Zorro II card into. It also has a standard floppy power plug and circuitry to choose this supply if provided, otherwise use power from the Amiga itself.


The collation of parts was pretty straight-forward, and I only made one mistake! The relays I'd purchased were much too large for the PCB holes.


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So I used a relay I had on hand. It didn't work once soldered and tested... it was rated for a 24-volt input! So I went ahead and re-ordered the correct part.


Next up, I used a spare molex power supply plug to make powering the card a little easier...

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Final notes when building... after you've soldered nearly 200 joints, go over them all with a magnifying glass...


It's really easy to miss a soldered join when the plates on the PCB are so shiny... also when the lighting above is LED and the reflections of the melted solder look more 3D than they really are! Fully inspect each joint, otherwise you'll get grey screens, white screens and even half-booting!

The shot above shows one of two pins that I failed to correctly solder, and note that it shows it after I found it and slightly bent the pin to test that it wasn't actually making contact! The actual hardware symptom was that, whilst booting, the drives would be found, Workbench would start booting and then it'd pause at the 'wait timeout' in the StartupII boot script. I assume there's some interrupt or IO signal that's meant to come over that pin... amazing how random things are when signals aren't correct.

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Finally, the board was assembled and ready to test!

MegaMicro Technologies: SCRAM 2000

SCRAM 2000 is a SCSI for A2000, A3000, A4000. And now also the Amiga 500! This board features a board-mounted 3.5" SCSI hard drive, an external DB-25 SCSI port and the ability to host a total of 8mb RAM.


The card came without a SCSI drive, so I grabbed a 40mb Seagate SCSI (from Apple!) from my box'o'crap, set the ID to 0 and mounted it to the card. Note that the spacing is very tight for the data cable, so make sure the wires are leading away from the card when you plug them in...


After a lot of toying around, the disk was mounted, formatting and even auto-booting on my KS1.3 Amiga! I used a boot disk instead for the KS1.2 Amiga. Note that the install disk can be used as both. Grab it from here and use ScrapPrep to get your drive in order. Then you just need to copy over the Workbench disks and make sure the boot priority is the highest amongst all drives connected! Check out this post for more details on bootable drives (disregard that it's about IDE drives!)

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A fun note on this card... it would've actually come in kit-form to the original purchaser back in the late 80s. When that user assembled it, they put the three status LEDs in backwards. I was wondering, whilst debugging things and trying to work out why my machine wouldn't load, why the LEDs just didn't light whatsoever. I assumed it was because I was using a KS1.2 machine and there was no config, etc.... but it turns out that the LEDs were actually in wrong. I fixed this and also rigged up a LED to use on the activity LED headers... a much quicker way to test things like this!


Next trick was to upgrade the RAM on-board. The board uses ZIPs and this was my first time encountering them. Just think of an IC standing on one side, with all pins out the bottom edge. They're interleaved and you must make sure that they line up correctly before inserting them!


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As is my usual rush.... I happened to put the last chip in backwards. With the card inserted, the machine wouldn't respond at all... no power light, nothing! I had only ordered 16 chips, so I was very fortunate that everything 'just-worked' when I swapped it around.


Finally, you'll note that the external SCSI port was nicely corroded on the board I recieved. A quick trip to Jaycar saw the purchase of a replacement part and, after a little destruction, the new port was soldered in place.

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After this, I had a perfectly bootable SCSI A500 system with 8mb of Fast RAM!

GVP HC+8 Series II, Revision 2 Zorro II SCSI Card

This card happens to be very similar to the SCRAM above. It also hosts 8MB of RAM and a SCSI controller with an external SCSI port. The main difference here is that drive is mounted the opposite way around and SIMM RAM is used.


This first thing I did was get the RAM situation sorted out. The card came with 2 SIMMs installed and the auction quoted that this was 2MB of RAM. I threw the card in the system and the top line of WorkBench 1.3 indicated just under 3MB as the A500 has 512kb internal and the was also a 512kb expansion card in the trapdoor slot. With this, I tried to do things and kept getting the crash below...


I thought I'd bought a faulty card until I pulled the two SIMMs out and realised that they were only 256kb each! The Amiga was trying to get to the other 1.5mb of RAM and there was physically nothing installed... no wonder it crashed. I quickly populated this with 8 1MB RAM SIMMs and the machine soaked them all up, testing them out perfectly.


This one also had a corroded external SCSI port, so I went ahead and replaced it as well.

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Finally, a few shots to show what SysInfo has to say about the card.

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Installing an setting up the drive was just as simple as the SCRAM setup. the GVP software works beautifully and you can grab the setup disk here, but but here it is as an ADF.


Just make sure that the HDD is not grounding on the ground-plate of the power regulator!

SupraDrive 2000 WordSync

This card is still on its way from the US of A. As mentioned on the Amiga Hardware Database, this card uses two 8-bit transfer buffers instead of DMA. The card is noticably more simple with regards to chip count and board complexity. It's also half-size, not taking the full length of an A2000 case... so I might even try and shoe-horn it into a nice side-car style box.

I'll update more when it has arrived.

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  1. Awesome post :o) Do you have a part number for the regulator? The BOM mentions a “7905TV” (Negative voltage regulator). I’m looking into a Zorro graphic card, any thoughts?

    • Hi Keith,

      It’s definitely a -5v regulator. The standard side-car slot peripherals don’t use/need the -5v, but Zorro II cards do, and since it’s not available, needs to be created for them.

      I can’t confirm if a video card will work in this slot. I’ve only tested RAM/Storage.


  2. Amazing post really interesting & very helpful, also wanted to thank you for help on the relay part number!

    • Hello Steven

      Sorry to bother you but I am also building one, the only odd thing that I don’t understand is why on the silk screen on caps C6 & C3 the positive marking is really ground or am I missing something as it negative rail?, sorry for the question, as all pictures I see show these caps installed backwards.

      Many thanks

      • Hi Keith,
        The capacitors are labelled and installed the correct way around.
        The 7905 is a negative voltage regulator. Therefore, the output is negative and the filter caps need negative to the input/output of the 7905 and positive to ground.

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