Sometimes I want to show how old 8 bit computers work for some n00bs. It is nice to load some games from tape, some from disk. But when I want to show more games, the best thing is cartridges. And not a single universal cartridge, but a pile of them. This looks more “expensive” and cool.
Another reason- cheap PCB and that I wanted to go in this way.
And the main reason for cartridges is speed- just put in and power on. I never liked this game.
This universal PCB for Commodore 64 cartridge. For more advanced cartridges there is mandatory to add two chips- simple logic and flip-flop. I used a single chip- GAL or PALCE. I have several of these and have programmer. For standard 8K or 16K games there is no need for additional chips. Only some jumpers and two diodes.
I always had problems with 3D positioning my designs. Sometimes I am building mirror or upside down versions. At this time everything is ok and the cartridge fits properly.
Maybe there is a question why I put two resistors on the clock line. There are rumors that on some models of computers it is good to place proper TTL termination on the F2 (CPU clock) line.