After further debugging, my monitor for the Apple 1 with MC6800 microprocessor now works, at least on the MESS simulator. I’ve used it to examine and modify memory, and to run a small test program in RAM.
The monitor still needs to be tested on real hardware, but now I have high confidence that it will work. The monitor is exactly 256 bytes long, the maximum that will fit in the two 256×4 bipolar PROMs used in the Apple 1.
I tried to record video of the session with MESS’ built in avi capture feature. I get an avi file that is hundreds of megabytes, and I haven’t been successful at transcoding it. The worse problem, though, is that the video is rotated horizontally, so that what should be at the left edge of the video is actually almost at the very right edge, and wraps around.
I guess I’ll have to use a camcorder to capture a session.