The Expansion unit only has 6 slots and one of those is occupied by the connection to the One. One is required for the Floppy Disk Drive controller and another was occupied by the Hard Disk Controller, but that has been swapped for an XTIDE. Another was occupied by a printer card. Then i added a CGA card. One slot remained.
I really wanted to add a game port and a couple of IBM compatible serial ports (ideally one for a mouse and one for Kermit serial communication); the native com ports are not compatible. The easiest way to do this is to replace the original printer card with a multifunction card and an additional I/O panel. It may be possible to use the multifunction card’s floppy disk controller in place of the original, but i have disabled it for now.
I have used a CA9342 multifunction card. This card is 16 bit, but i expect that the 16 bit operation is limited to IDE, which i won’t be using. I disabled IDE and FDC. Obviously it is from a later era, but so is the XTIDE card. It could be replaced with an older card – one that could provide another 128kB of RAM would be interesting.
The Serial Ports were set to COM3 and COM4. This will provide two PC compatible com ports. The printer is set to LPT1 and the game port is also enabled. The second serial port and the game port connectors are mounted on a second I/O panel.
| Parallel port enabled | JP2 | pins 1 & 2 closed |
| Parallel port disabled | JP2 | pins 2 & 3 closed |
| Serial port 1 address 3F8 – 3FFh select | JP3 | pins 1 & 2 closed |
| Serial port 1 address 3E8 – 3EFh select | JP3 | pins 2 & 3 closed |
| Floppy drive interface enabled | JP4 | pins 1 & 2 closed |
| Floppy drive interface disabled | JP4 | pins 2 & 3 closed |
| Serial port 2 enabled | JP5 | pins 1 & 2 closed |
| Serial port 2 disabled | JP5 | pins 2 & 3 closed |
| Parallel port address 378 – 37Fh select | JP6 | pins 1 & 2 closed |
| Parallel port address 278 – 27Fh select | JP6 | pins 2 & 3 closed |
| Serial port 2 address 2F8 – 2FFh select | JP7 | pins 1 & 2 closed |
| Serial port 2 address 2E8 – 2EFh select | JP7 | pins 2 & 3 closed |
| Game port enabled | JP8 | pins 1 & 2 closed |
| Game port disabled | JP8 | pins 2 & 3 closed |
| Serial port 1 enabled | JP9 | pins 1 & 2 closed |
| Serial port 1 disabled | JP9 | pins 2 & 3 closed |
| IDE interface enabled | JP10 | pins 1 & 2 closed |
| IDE interface disabled | JP10 | pins 2 & 3 closed |
| Serial port 1 interrupt is IRQ3 | JP11 | pins 2 & 3 closed |
| Serial port 2 interrupt is IRQ3 | JP11 | pins 1 & 2 closed |
| Serial port 2 interrupt is IRQ4 | JP12 | pins 1 & 2 closed |
| Serial port 1 interrupt is IRQ4 | JP12 | pins 2 & 3 closed |
| Serial port 1 interrupt is IRQ5 | JP13 | pins 2 & 3 closed |
| Serial port 2 interrupt is IRQ5 | JP13 | pins 1 & 2 closed |
| Serial port 1 interrupt is IRQ2 | JP14 | pins 2 & 3 closed |
| Serial port 2 interrupt is IRQ2 | JP14 | pins 1 & 2 closed |
| Parallel port interrupt is IRQ7 | JP15 | pins 1 & 2 closed |
| Parallel port interrupt is IRQ5 | JP15 | pins 2 & 3 closed |
I ran checkit to check the configuration.
MS-DOS 5 does support COM3 and COM4 but can’t see the native One ports, so it labels COM3 and COM4 as COM1 and COM2, respectively. Checkit calls them by names based on their addresses. COM4 (that’s what you type into Kermit) works under MS-DOS 5 but COM3 does not. It only transmits.
MS-DOS 3.2 does not support COM3 and COM4 but Kermit still allows them to be selected, albeit with assumptions about addresses. I found the COM3 worked fine, but curiously COM4 would only transmit.
Once again the IBM incompatibility makes everthing flaky. Checkit reports a missing interrupt. It is what it is.
The joystick shows up and tests fine in Checkit. It does not always work in practice. It works great, for example, with Cosmic which is a space invaders style game.
