4 player adapter for Commodore 64/128


This little adapter plugs to the user port of the C64, C128, VIC-20 or CBM 610 computers. Here is a list of some of the games that support this adapter:
    • Alone in the Green
    • Amazing Maze
    • Bomb Mania
    • Garrison
    • Hockey Mania
    • IK+ Gold
    • Marble Madness
    • M.U.L.E.
    • Pac It
    • Phong!
    • Quadris
    • Quadtron
    • Rampage Gold
    • Snacks 4 Snakes
    • Space Lords
    • Square Attack
    • Ivan ‘Ironman’ Stewart’s Super Off Road
    • Tanks 3000
    • Team Patrol
    • Tour de France 2005
When I made this, I wanted more than just to add 2 more joystick ports.
Since a lot of C64 models does not support a reset via the serial port. (I made the Pi1541 with a reset button on the serial port) I figured I should at least add a reset button on this device. Using the user port to reset the C64 is probably the safest and easiest way to ensure a reset that works on all models. But, I did not stop there. The user port is also a port that connects to both the internal AC 9V, and the DC 5V. So I made one LED for each of these power rails, so that this module can be used to verify if the computer actually gets any power. When the power light on the computer lights up, it does not mean that the AC 9V is working, and to test it, you will have to open it up and do the measurements manually. Measuring the PSU at the plug is risky business, since a slip can short your PSU. Now, all you have to do is to plug this in to verify that the power is working. Since LEDs use power, and might be annoying, I made sure they can be disabled with a jumper too. Notice how none of the other 4 player adapters have all these features! Most don’t even have pullup resistors!
This one is FULLY LOADED!
Why a reset button?
The reset button is useful in several ways. For a gamer, it is handy is if you have some resident code in high part of the memory, beyond what many programs use. For example “Turbo Tape 64” relocates itself to SYS 50000 [$C350] which mean after loading a game with the turbo, you can often hit the reset button, type in SYS 50000 and the turbo was reenabled and ready to load the next program. Of course if the loaded program extended beyond this address you would have to reload the turbo program from tape or disk.
A reset button will retain almost all the RAM contents, so you can recover from a crash. Powering the computer off and on will clear the memory completely
Another use would be to enter cheats to games, which came as POKEs to various locations in memory to give you infinite lives etc., with a SYS call to restart the game.
As a coder: Hit the reset button and sys 32768 and you are back in Turbo Assembler. All other resident programs would still be there, like a tape turbo. Best of all, you’d keep on hacking the night away without having to reload your source.

2x D-SUB 9
2x LEDs
8x 10k Resistors
1x Diode
1X 220R resistor
1x 1k resistor
1x Custom PCB
1x 100nF Capacitor
2x Jumpers
2x 2 pin
1x Tactile switch
1x User port connector
1x Data Selector/Multiplexer

This project with PCB and parts can be purchased on ebay:  https://www.ebay.com/usr/kirsti_73
or from Sellmyretro.com