Moving to Board
Wire wrap sockets and wire have gotten expensive. I’ll have to order some later. So for this project I’ll have to stick with soldering. It’s slow work.
The first thing I did was wire all 60 signal pins and power to a female pin header. This will let me test each new part of the circuit on a breadboard before soldering it into place – an important step I’ve forgotten too many times in the past.
I’ve drawn up a schematic in Eagle with things I would like to test, based on what I have on-hand already: 64k of SRAM, Zilog Z8530 Serial Communications Controller, Compact Flash in IDE mode, and of course an ISA-like interface for my LED display board. If I have room left on the board, and can figure out the logic, I have some 30-pin SIMMs I’d love to throw in.
From the schematic, I like to draw a functional diagram in the style of the one Daniel Kottke drew for the original Macintosh. I use graph paper, with one square representing four holes on the board. I’ll mark out the box of each chip and name each signal. I find it much more useful than a traditional schematic when actually building something, and it lets me plan how everything will fit on the board. I arranged the RAM, ROM, and register several times on paper to optimize wiring based on proximity. I’m sure I could do that in Eagle too, but sometimes I just think better putting pencil to paper.
