This is an old post, preserved for reference.
The products and services mentioned within are no longer available.
I'm currently working on a VIC20 cartridge with an assortment of features, and as that is progressing, I have made a few prototype boards testing different features. The first of these was a general proof of concept, to test the practicalities, and was a VIC20 ROM and RAM expansion.
Commodore 64 diagnostic cartridges, this needs a diagnostic test harness to fully test the machine. The original has been reverse engineered by Ray Carlsen with various pictures here, and also on zimmers.
Dave Stevenson, which allowed the 2532 to be programmed with my EPROM programmer set to 2732.
Stack IEEE-488 cart I tested previously. I've reverse engineered the design and then simplified it (and reduced the chip count) by using 75160 and 75161 buffers. There is also 32K RAM under the ROM chip and provision for a diode in the IRQ line of the 6522 should that prove necessary for WDC chips.
PET microSD into a single cartridge, 'the Penultimate Cartridge'. That's going to be quite a challenge, so I am testing out all the elements separately first.
Anders from Sweden has uploaded a video demonstrating VIC20 diagnostics using one of my VIC20 ROM/RAM Cartridges.
ROM/RAM cartridge is now finished (and that went on to become the Penultimate Cartridge).
2022 Update: The production version of the Penultimate Cartridge is now available from The Future Was 8 bit