PDP 8 Timesharing

Jay West jwest at classiccmp.org
Mon Nov 30 15:07:37 CST 2015

Glen wrote...
If you have a 2113B and a 2117F could you use those as a base? What are the magic parts? Some special and rare interconnect boards? And a special and rare async mux? And particular disc requirements?
2113/2117 - yes.

Off the top of my head....

For 2000E, you can get by with a single cpu, paper tape reader, and 7900 disc drive (non HPIB). That's the smallest config likely to be runnable by folks (unless you happen to have a drum unit or fixed head disc for prior versions). And the mux set below....

For Access (by far the best version), of course two cpus, mag tape (non-HPIB), and disc (again, non-HPIB) are required. 32kw in the main cpu, from 16kw to 32kw in the IO cpu depending on sysgen choices. I believe one of the processors needs FPP, have to check that. But the magic bits...

1) You'd need the IOP microcode. This is downloadable from bitsavers for 21MX/E and you can burn them. I can get people burned chips if they wish. For the M series, you need the microcode AND a daughterboard to put them in :) For the 2100, I have the microcode - and I'm not aware that those are available anywhere else. In most - possibly all - situations the iop firmware must be on a fab (E/F). Trying to put it in a FEM may (have to check, I think it will) cause issues with hard coded slot assignments in the IOP.

2) You'd need the processor interconnect kit. Basically this is 4 (two per cpu) 12566 boards and you'd have to build or find the cables for them.

3) MOST difficult... you need the 12920A or 12920B mux set (3 board set). These are unobtainium.

4) If you want to enable the IBM MRJE facility, you'd need the sync modem (2 board set). Pretty rare...


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