After far too long, I managed to prepare a first version of the front panel schematic, and it turned out to be a monstrosity, sprawling over seven sheets of A3. Most of the estate is taken by LEDs, current limiting resistors and buffers. There are over 50 ICs on the board, and there's no chance I can route this on the Hobbyist version of Eagle. Thankfully, the design can really be split up into a number of components.

• Switches
• LEDs and current limiting resistors (and a little bit of display-specific logic)
• LED buffers and headers to the LEDs
• Switch debouncing and logic
• Front panel system device (the HALT instruction, Switch Register, optional dip switches, and Output Register)
• Front panel sequencing (signal encoders for the examine/deposit functions)

Some of these will have to move close to the sources of the signals they use. The IR register header has to be close to the IR, the AC header will be close to the AC, and so on. In some cases, the boards are too overpopulated for the buffers, so another solution may have to be devised. Possibly small daughterboards with the buffer and an IDC socket.

Another option is to build the entire panel, switches, LEDs and all on one or two huge prototyping boards, bite the bullet and just wire it all up there. With a little bit of luck, the cables connecting the buffers to the processor will be short enough to avoid transmission line effects. In which case, since the front panel is fairly independent of the rest of the machine, I can start building it soon.