Intel Intelec MDS-800 Restoration

8/6/22

We slowly powered on the system using a Variac so we could reform the large electrolytic capacitors in the power supply. We connected it to a dual-drive double-density 8" floppy diskette system and used a PC for a console CRT. The system would load the ISIS-II bootloader from diskette, configure the baud rate for the console, and then do nothing. We swapped Monitor Module from MDS-800 #1, but there was no change. We swapped the pair of RAM boards from MDS-800 #1 and it booted ISIS-II. So now we know that everything is working except for one of the RAM boards. Debugging and repairing the RAM will be the next project.

This system came with a large collection of development software on diskette. It looks like we have assemblers and PLM compilers for the 8051, 8080, 8086 processors.

Notes:

The ISIS-II boot sequence is:

Press the top of the BOOT switch
Press the RESET switch
The drive 0 select LED goes on, the diskette head is loaded, the head is retracted to track 0
The Interrupt 2 LED goes on
Press the Space Bar on the terminal
The Interrupt 2 LED goes out and the diskette head unloads
Press the bottom of the BOOT switch
The diskette head is loaded, the heads move a few tracks, and ISIS-II is loaded

ISIS-II diskette listings go here.

To Do:

Update the MDS-800 #2 page with pictures of the boards, and a detailed list of the configuration.
Debug and repair the RAM boards.