For the past couple of weeks I’ve been developing an automated tester for Yellowstone. My goal is to streamline the program and test process for Yellowstone beta cards, and eventually for the first production run. The ugly tangle of wires shown here may not look like much, but I’ve used it to successfully program a card with a blank FPGA, and to simulate 6502 bus cycles for reading and writing from the card’s memory. I was surprised to discover that those looping crisscrossed wires still work reliably even at speeds as high as 10 MHz. I was also able to measure the current consumption of a Yellowstone card at idle, plus the test hardware itself, which is about 80 mA. That’s lower than I’d guessed.

I think I’ve stretched this breadboard prototype about as far as it will go, even though many things remain incomplete. There’s still no testing of the disk drive interfaces, nor have I implemented any of the short-circuit detection that I discussed here previously. Those pieces will have to wait for the final version of the tester, when it’s built into a nice PCB instead of a snarl of loose wires. My next task is to take what I’ve built on the breadboard here, and convert it into a PCB, and add the missing elements for testing drive interfaces and short circuits. There’s still a lot of software to write as well. I’m guessing the whole process may take about four weeks, including the PCB manufacturing time.

Once that’s done, I can hand-assemble a few Yellowstone beta cards and use the finished tester to program and verify them. If all goes well, I may be able to wrap up Yellowstone development by Halloween.