The video emulates the 25x25 display with the unseen video memory addressable exactly like the OSI 600. A 32x28 mode gives more screen characters and I'm working on how to switch between the 2 modes. The 28 lines is the most that can fit on the video display. 32K onboard RAM gives plenty of memory to go around.
The cassette may or may not be available. I'm working on that but I left it as an add-on board for now. a 3.3V-5V buffer will be required to use original OSI 600 hardware. I also but a cut away section for the BREAK key to hardware an external switch but may change that to a small tactile switch combo with BREAK. This would prevent accidental RESET of the board (been there already).
The keyboard caps were created by me using WASD key caps and Cherry MX switches. The SHIFT LOCK is locking but I only have a few of these. Once these are gone, a standard key switch will be used but a slide switch will handle the SHIFT LOCK functionality.
Let me know what you think so far. I'm trying to do a final prototype by May and get something going by June. I will do a small run of 20 units to start. The size is 11"x8".

Here's my OSI 600 Superboard II that I used to help develop this project:

