What card are you hooking up the splitter to? Could be that the issue is there, unless you know for sure it does behave well with other second controller devices.

My guess is the second pad is not getting +5VDC. Most joystick splitters would have been designed for analog sticks which don't require power for the axis like digital gamepads do

Get yourself a multimeter and measure out the wiring .

dionb wrote on 2022-07-26, 07:55:

What card are you hooking up the splitter to? Could be that the issue is there, unless you know for sure it does behave well with other second controller devices.

I tried my Vibra16 and my Sound Blaster Pro 2, neither worked.

And I do not know where I would even begin measuring the wiring.

found a little table on this page https://www.pccables.com/JOYSTICK-DB15-Splitter-Y.html
usable for reference while measuring which pins needs to connect to which pins

tomexplodes wrote on 2022-07-26, 03:47:

I also tried the gravutil program to test, and port one registers X, Y, and both buttons. Port 2 registers X as all the way to the right, Y as nonexistent, and neither button does anything. I can however move X to the left. This seems off. I would expect at least the pad to work, and I could swear that you're supposed to be able to use 2 gravis pads if they're set to 2 button mode. SO. Did I get a faulty splitter?

There are two pinouts for the game port. The classic pinout and the MIDI-capable pinout. Every sound card that supports MIDI in/out in the game port uses the MIDI-capable pinout. Every splitter designed in the 90s vor later should be compatible with the MIDI pinout. Your symptoms sound linke you got a splitter designed for the 80's wiring scheme of the pinout.

The 80's scheme had three dedicated voltage supply pins for the second joystick that were not shared with the first joystick. There is no technical need for dedicated supply pins, so when they added MIDI, two of the three supply pins were repurposed as MIDI pins.

The +5V supply pin for the second Y axis became MIDI OUT (pin 15), and the GND supply pin designed for both buttons on the second joystick became MIDI in (pin 12). There are still three +5V and two GND pins on the MIDI-capable pinout, so a decent splitter would pick Y supply and button ground for the second joystick from some other pins than the repurposed pins.

If your splitter is designed for the classic pinout, it should work with game ports on ISA multi-I/O cards. Be aware that a lot of ISA multi-I/O cards went the cheap route and omitted support for the second joystick, or at least the analog axes of the second joystick. Two axes can be implemented using a single NE556 chip, a very common and extremely cheap chip. Four axes would need either two of them or the less common (and thus more expensive) NE558 chip. NE558 chips were used so seldomly that most distributors stop having them in stock at all, whereas the NE555 and NE556 are typically available everywhere.