Intel MCS-85 Restoration

4/17/2021

Reseated all of the chips because the MCS-85 would not reliably run.

Made a cable to connect an ASR-33 Teletype to the MCS-85, and replaced the jumper that determines if the keypad or the Teletype is used as the console. Now we can save and load programs to/from paper tape. To use the Teletype, the board must be reset while the terminal is already connected and the switch has been set to TTY (up, on this particular example).

The Molex connector and pinout matches a DEC VT-220 terminal, and all of the Teletypes at the RICM.
The pinout for the Terminal/TTY cable:

4/24/21

Tried the other MCS-85 board we have because the bus section on that one is populated, but it wouldnt boot.

Added a socket for the second 8155 chip, which allows the installation of another 256 bytes of RAM. Took the RAM chip from the non-functional MCS-85 board and installed it on the restored one.

removed the old speaker and cleaned off the glue to reclaim some space on the protoboard area. Replaced it with a small piezo buzzer.

Tried to load a simple program, but wasnt able to get the 8080 assembler working on a laptop. Will try to have some assembled programs to enter next week.