While there are documents out there that describe the function of the Educomp/Quodata TSC8-75 Timeshare System Controller for Omnibus PDP 8 machines, I have searched high and low, and there doesn't seem to be /any/ schematics for it anywhere.
I know this was a proprietary board that did some pretty interesting things to trap IOT, JMP, JSR, and HLT/OSR instructions on the PDP 8/e/f/m/a machines and provide additional capabilities versus DEC's Memory Extension and Timeshare Control board. I have a fantasy of being able to run ETOS on real PDP 8/e hardware, but I don't have one of these boards, and they seem to be pretty much unobtainium. There are a few of them out there, but obviously, the owners of these aren't in the mood to submit them for reverse engineering. Perhaps someone out there has already done this, or someone has documentation on the board that may include schematics that simply hasn't scanned it yet. Bitsavers comes up with nothing under the DEC archives, and there's no sign of Quodata or Educomp folders. I have read the descriptions of the function of the board, and the IOTs that make it do its things, but I just don't have the expertise on the guts of the Omnibus PDP 8 machines to be able to take this information and create a design for a board that performs these functions. I've also looked at the code in SimH that emulates the functionality of the board, but again, it isn't enough information for me to be able to figure out how to implement it in hardware. In any case, I think it'd be interesting to see if one of these boards could be reproduced. I've found some old ClassicCMP list archives that mention some stuff about ETOS documentation and folks that worked for Educomp/Quodata that were involved in the creation of ETOS and this board, but the thread died over 10 years ago. I am probably wishing for something that doesn't exist, but I figured I'd ask anyway, as maybe someone has stumbled across some of this stuff and just hasn't made it public yet. Rick Bensene The Old Calculator Museum http://oldcalculatormuseum.com
