This is an old post, preserved for reference.
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The last version of the VIC20 Penultimate Cartridge I'm currently working on expanded the ROM and RAM capabilities, but at the cost of increasing complexity. There were now 9 DIP switches (soon to be 10), 4 to select the ROM and RAM mode, and the rest to select a ROM image set. This came with a long table of the ROM and RAM setting required for each ROM set. For example, you would need to set mode 1 and ROM image 0 for Avenger, and mode 9 and ROM image 8 for the diagnostics cart etc. This worked fine, but would be a bit annoying to use, keep having to refer back to the settings list, which was too large to print on the cartridge case.
- POKE 38928,X - change to mode X imediately
- POKE 38929,X - change to ROM address X imediately
- POKE 38930,X - change to mode X, apply pending ROM change and reset
- POKE 38931,X - preset ROM address for above
This should cover most of the options required. The menu should be able to offer things like
- Run a game cartridge from ROM (8K/16K/Atari 16K/Scott Adams 16K)
- Run the VIC20 diagnostics software (which needs ROM and RAM)
- Run Super Expander or other BASIC with up to 27K RAM
- Exit to BASIC with 3K-35K RAM
But also I think I should be able to get it to run some commands on reset,
- Exit to BASIC with 3K-35K of RAM and execute LOAD "*",8
- Exit to BASIC with 11K-35K of RAM and execute LOAD "FB20-8K",8
- Select a Scott Adams adventure and execute SYS 32592
Being able to autostart a diskimage or the file browser on an SD2IEC (or a 1541 if you like), would be a nice feature to have, and avoiding typing SYS 32592 makes the Scott Adams adventures easier to use.
The new boards are here, the software is taking a bit longer to write.
I have some simple single ROM cartridge PCBs, if you only want to replace a single game.
If you like DIP switches, I still have some of the current version of the PCB available, built and tested with up to 35K RAM and 32 ROM images:
The menu software has been rewritten in C.
Update 4: Penultimate Cartridge V4.3 available now, all menu driven, no DIP switches.
2022 Update: The production version of the Penultimate Cartridge is now available from The Future Was 8 bit