I completed my original RetroChallenge project, the rewrite of the Apple 1 monitor for the MC6800 microprocessor, sooner than expected, so I’ve spent my spare time for the rest of the month working on HP-41 calculator stuff.
I analyzed bugs in the microcode of the HP-41 and card reader, reverse-engineered portions of the Extended I/O ROM, and made a lot of progress on the DIY4 calculator which runs the original HP-41 microcode.
I may do a little more today, but don’t expect to have any additional significant progress to report by the end of the day, so I am declaring the project a success. It will remain to be seen whether it is judged worthy of a prize, but regardless of that, I am happy with what I’ve accomplished. I wish I could get this much accomplished in my spare time every month!