Just my observation....Back in the XT era game ports rarely allowed two joysticks for multiplayer gaming on same computer without need of splitter cable. I think these allow two simple 4 axis two button types to work without a splitter.
Yes they may work to use along side MIDI but only experimenting will tell. The XT/PC switch maybe changes the timing (known issue is fast AT's can cause issues with a Joystick port, or could be something else).
Different rev's might be the diff of different resistors...
That is all I got on quick look over...

All the resistors that are present on all three boards are the same value.
1 board that is missing components has two HCT chips in stead of LS, this board has 4 yellow-ish capacitors
1 board has that is missing components has 4 blue-ish capacitors
1 board has 4 what looks like pink-ish resistors in the place of the location of the other two boards where the capacitors are located, and has 4 more what still look like green resistors (coils?) .

likely supporting a total of 4 axis, two per joystick, and 4 buttons, also two per joystick.

Any chance of a photo of the backside ?

Capacitors are all same value ; the greenish components are inductors ; differences between HCT & LS are small and various (consult datasheets)

Horun wrote on 2023-10-15, 02:36:

Just my observation....Back in the XT era game ports rarely allowed two joysticks for multiplayer gaming on same computer withou […]
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Just my observation....Back in the XT era game ports rarely allowed two joysticks for multiplayer gaming on same computer without need of splitter cable. I think these allow two simple 4 axis two button types to work without a splitter.
Yes they may work to use along side MIDI but only experimenting will tell. The XT/PC switch maybe changes the timing (known issue is fast AT's can cause issues with a Joystick port, or could be something else).
Different rev's might be the diff of different resistors...
That is all I got on quick look over...

I'll probably install it in a Pentium MMX 233 system (I'm running it at around 150Mhz instead to help with speed sensitive games)

weedeewee wrote on 2023-10-15, 11:18:

1 board that is missing components has two HCT chips in stead of LS, this board has 4 yellow-ish capacitors

Oh yes. Good catch.

weedeewee wrote on 2023-10-15, 11:18:

Any chance of a photo of the backside ?

Sure.

giantclam wrote on 2023-10-15, 11:51:

Capacitors are all same value ; the greenish components are inductors ; differences between HCT & LS are small and various (consult datasheets)

Should be great to have some of these remanufactured. Some might find these card useful. This design sould be very easy to clone. A few 74xx chips, a quad timer and a few passive components. Simple PCB.

One backside was enough since they're all the same pcb. 😀
the PC/XT switch might just be to handle the ISA bus speed difference. 4.77MHz/8MHz (or vice versa).

Could you measure the pink-ish looking resistors to see if they're resistors or some kind of capacitor ?

weedeewee wrote on 2023-10-15, 14:11:

One backside was enough since they're all the same pcb. 😀
the PC/XT switch might just be to handle the ISA bus speed difference. 4.77MHz/8MHz (or vice versa).

Could you measure the pink-ish looking resistors to see if they're resistors or some kind of capacitor ?

Resistors.
I tested the pink ones and the yellow ones that are at the same place on another card.

All values are around 860 ohm if my reading is correct.

must be in parallel with something. Those yellow ones are for sure capacitors, same as the blue ones.
Though... i'm not getting what could get you a resistance value of 865... curious.

Seems to me to follow the standard imb gameport circuit + the AT/XT switch ... https://cosmodoc.org/topics/joystick-function … apter-2052x.png