link: http://www.glitchwrks.com/2018/08/30/3ps-imsai-sio I recently repaired a Processor Tech 3P+S I/O board for the VCFed Museum. This 3P+S is going in an IMSAI, so it was to be configured as compatible with the first channel of an IMSAI SIO-2. The 3P+S is a super versatile I/O board, much of the configuration is left to the user to jumper in as they want, but making it look like an IMSAI SIO-2 did require a cut-and-jump. But, after fixing the control/data register ordering and taking the bitrate base clock from the 2 MHz pin (pin 49 on S-100) instead of the system clock, it works! I was able to pull my IMSAI SIO-2, drop in this modified 3P+S, and run the software I'd been running on the SIO-2. The 3P+S is on my short list for "S-100 boards to reproduce." It's a very handy serial interface, being as how it can be made to look like most other manufacturers' boards. Thanks, Jonathan