Throttle Expansion.

Description of how to add four more throttles to your TMWDCC Command Station.

How a gameport functions.

The PC have I/O address 0200-020F reserved for use by game cards. All game cards respond to calls on address 0201, and some cards respond to calls on address 0200-0207. The PC is not designed to handle more than one game card. However, we do need two cards to operate our eight throttles. We have to add a card in a way that it does not upset the PC. Then the TMWDCC program will look for throttles number 1-4 on the first card on I/O adr 0201, and for throttles number 5-8 on the second card on I/O adr 0208.

How to modify a game card to respond on I/O adr 0208.

Use a game card that can handle two joysticks. If you use a card that can handle only one joystick, the modified card can only handle two throttles. If the game card, that you are going to use as game card 2, contains other controllers than the game controller, they have to be disabled, (serial ports, parallel ports, floppy interfaces, HD interfaces, sound controllers, or whatever). Have a look in your manual for the card, how to do that.
Have a look at the pinout of the I/O card slot on fig 1 and fig 2. I will upload a better gif later, showing the modification.
We are going to swap the traces that run to pin A31 and A28. It is as simple as that. Cut the trace heading for A31 and solder a wire so it ends up at pin A28 instead. Then cut the A28 trace and redirect it to pin A31. Now the card responds to calls on adr 0208 instead of 0201. Plug the card into your PC, load the dcc-mbx driver and run the tmwdcc program. Now when you connect a throttle to the second game port, the lines "throttle number 5-8" should appear on the screen. Then calibrate the throttles, and you are ready for operation.