It’s not uncommon to find modified Epyx Fast Load cartridges. This cartridge was super popular in the 1980s, but there were generally one or two reasons to modify it by adding a button, a switch, or both to it. Both were common Epyx Fast Load mods to make the cartridge more useful.
Usually a switch on a Fast Load cartridge is intended to disable it, while a button is probably to reset the computer. Both were common modifications that tech-savvy owners made to save wear and tear on their computers.
A switch to disable Fast Load
Some games didn’t work with the cartridge. And while you could disable it by hitting the £ key on the keyboard and then hitting the letter D, some stubborn games still wouldn’t work with the cartridge plugged in. The only recourse was to unplug the cartridge.
Or, if you didn’t want to wear out the cartridge and the port on the back of the computer, you could install a switch. At least two different magazines published instructions for doing this: Commodore Magazine, in June 1988, and Transactor magazine, in January 1987. Both magazines recommended you cut the trace that leads from pin 9 of the cartridge connector somewhere on the circuit board, then solder an SPST switch to both sides of the cut and mount the switch either on the top or the back of the cartridge.
An alternative way to do it is to cut pin 8 on the 7407N chip on the board that connects to the trace, wire the pin to one leg of the switch, and wire the other leg of the switch to pin 9 of the cartridge. This lets you avoid scraping away at the solder mask on the cartridge’s board.
Once you had the switch installed, you could flip the switch and power-cycle the 64 to make the cartridge invisible to games that didn’t like it.
Use with the Commodore 128
The disable switch became more useful when the Commodore 128 was released in 1985. Plugging an Epyx Fast Load cartridge into the 128 forces the 128 into C-64 mode. But if you have a disable switch on it, you can disable the cartridge when you want the 128 to run in 128 mode. There wasn’t a ton of software that required 128 mode, but people didn’t pay twice as much for a 128 just to run 64 software on it all the time. At least they didn’t intend to.
Installing the switch let you use the cartridge in a 128 without unplugging it.
A reset button for the Epyx Fast Load
The other common modification was adding a reset button. The reset button resets the C-64 without requiring you to power cycle it. There are lots of ways to add a reset button inside a 64, but you can reach a reset line from a cartridge, and most people preferred to solder and drill on a $35 cartridge than on a $150 computer.
To add a reset button to a Fast Load cartridge, you simply wire a button or a momentary switch between pin C (the third pin from the left on the underside of the cartridge) and pin 1 (the first pin from the left) on the cartridge edge connector.
Having a reset button is useful because you can press it instead of power-cycling the 64. This is easier on the chips inside the machine, and also on the power switch. Resetting instead of power cycling during a session extends the life of the computer.