However... complete doesn't mean finished. There will be continued iteration and refinement and then unknown problems to resolve during the prototype phase. After 37 days I have arrived at a design that should work and meet the current specification.

So the final numbers are in with a total of 54 chips. These break down as follows:

• 49 TTL
• 2 Memory (ROM, RAM)
• 1 RS232 line driver
• 1 Analog Switch
• 1 Op-amp

The gates still need to be shuffled around a bit and I may be able to consolidate with one less TTL chip. It's just as possible that this process could push the count up by one, so the TTL chip count is plus/minus one at this point.

I've also been working on some PCB layout ideas. I like the one-board approach of the Gigatron and it should be possible to cram the YATAC on to a board of similar size. I want to use a COTS enclosure though and this could become quite large and costly with a single PCB.

What became more apparent with a completed design is the natural demarcation between the GPU and CPU. The GPU requires a similar number of chips to the CPU and it seems a logical way to split the design to layout two PCBs.

The current plan is to place all the GPU logic, RAM, analog circuitry, clock generator, and connectors on one PCB. The CPU logic and ROM would be on a second PCB that mounts on top of the GPU using two headers. Each board would hold 27 chips in a target area of 18x12 cm. The entire assembly would then fit in a Polycase ZN-40.

Next up is a BOM and then placing an order for the prototype.