The CFT mini is meant to boot off a ROM (and, eventually, a hard drive), but I find I'm going to need a front-panel very early in the project. It doesn't have to be fancy, and it doesn't have to be complete, but it would help to have the logic in place now. A front panel is good for four reasons:

• I can use it to test and debug parts of the processor as they're built.
• It allows inspection of the computer's status.
• It's pretty much obligatory for any self-respecting minicomputer from the Sixties or Seventies.
• I like blinkenlights.

I had planned on designing the processor and then adding the front panel connections as nearly an afterthought, but I finally realised there are going to be lots of front panel connections and they're going to take a lot of board estate. So I stopped working on the CFT PCBs and prepared a first draft of the front panel and its circuitry. It was an eye-opening experience. There are 118 LEDs, 30 switches and 36 chips so far, and some functionality hasn't yet been drawn (notably, the memory and I/O deposit/examine logic).

Even worse, it looks like fitting the necessary connectors on the various PCBs of the processor will involve rerouting half the traces. I suspect it'll be such a hassle that I'm looking into alternative methods of prototyping that'll let me use bigger boards (my Not-for-Profit version of Eagle can route boards up to 160mm×100mm). So far, biting the bullet and rerouting seems like the cheapest and most elegant alternative. Though I may decide to do away with the Control Bus and connect the processor control signals locally. This will probably save enough board space for front-panel connectors.