IT LIVES! I spent most of today hacking on the 560Z board. I got the 12-bit porthole going first, took a bit as the manual doesn't tell you that you need IC CC installed if you want to be able to write to the 4K exposed in the porthole. After that, I plugged in a Z80 and tried to get it running the test code in the manual. Turns out I had a dud Z80 :) With a good one installed the test code ran no-problem, as did a little hand written code to push data to the lamp register on the new memory board. I plugged in an IM-6100 and pretty much determined that at least the first one I tried is dead. I'll recheck the soldering on it later -- it's stuffed into a machine pin socket and soldered in, since half of the legs were rotted off by that corrosive black foam everyone loves so much. Anyway, the second IM-6100 works! And the 560Z board works! And the 12-bit RAM board works! I made a (low-res, poorly focused) video with our old digital point-n-shoot: https://www.youtube.com/watch?v=ZYbGXHJST8U The IM-6100 is running a little loop that increments the accumulator and stores it to the lamp register. Storing of course clears the accumulator, but I have the lamp register mapped over RAM, so I just read the value back out of it. My first foray into PDP-8 code, it's certainly different, but it's still just machine code. Very happy that this seems to be coming fully together! Now if only I could find more IM-6100s...I'll test the remaining 3 tomorrow. Thanks, Jonathan