Making Cartridges for the Commodore C16, C116, and Plus/4

As I mentioned a while ago, I had the opportunity to repair a bunch of broken boards for Commodore C16 and Plus/4 computers. This led to a couple of new projects, the ROMulator and the PLA264. To help with the actual repairs, I built myself a Diag264 test harness.

All I wanted was a housing for my Diag264 cartridge, but it took me a few detours.

So, I also needed a cartridge to hold the diagnostic ROM. The Diag264 page suggests either modifying an original cartridge or using the OpenC16Cart. Destroying an original cartridge didn’t feel right, so I went with the latter option.

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How to Lower Your PLA: The PLA264

In my previous post I described in detail how I created a ROM replacement for the Commodore Plus/4 computer and how I made sure that it would fit into the very tight space of the closed case.

Five in a row: The four ROM chips of the Plus/4 to the left and the PLA to the right.

The four ROM chips of the Plus/4 are sitting all in one row, and then there is a fifth IC right next to them: the 251641-02 PLA. This PLA chip is the same for all TED based Commodore computers, the C16, the C116, and the Plus/4. In the past, I used the excellent PLA16V8 from D. Mantione as a replacement. The PLA16V8 is quick to build from cheap parts that are easily available. And for a C16 with it’s roomy case, it’s a perfectly adequate solution.

The original PLA16V18 is much too tall to fit under the keyboard of the Plus/4.

With the Plus/4, however, it’s all about space again: There are only a few millimeters between the original PLA and the keyboard above it. So while the PLA16V8 works fine on a Plus/4 motherboard, it is far too tall to fit inside the Plus/4’s case.

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Four at One Blow: The ROMulator

The Idea

Recently, I’ve been repairing a few broken and slightly weathered motherboards for Commodore C16 and Plus/4 computers.

Despite its stylish design, the Plus/4 was no success for Commodore.

When I ran out of spare parts, I replaced the defective Kernal ROM on one of the Plus/4 boards with a W27C512 EEPROM. You can still source a used W27C512 easily and somewhat cheaply (on eBay, for example), making it my all-purpose tool for replacing ancient parallel ROMs.

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