NaBloPoMo – DEC Micro PDP-11/73

YAPDP (Yet Another PDP).  Indeed here is another.  Its a PDP11/73.  It is a QBUS based system.  The 11/73 came out in the early 1980s.  This one spent its working life running custom software and a multi-user OS called TSX-Plus at a local pharmacy.  TSX-Plus actually ran on top of RT-11. Sort of like the early versions  of Windows using DOS to boot.  And this PDP 11 actually boots.  It is running RT11.  It has an RQDX2 drive controller,  KDJ11 processor board,  DEC memory, serial ports and Ethernet.  It is in a BA23 case with the proper rack mount hardware.  No games are loaded at the moment.  I guess I could go to my own website – RT11 Games at Saracom and get them.  Anyway,  here is some pics and Easter eggs too.  And a picture of the nifty RX50 5.25 inch diskette drive.  Space of two diskette drives but used one spindle motor.  You put the bottom diskette in upside down.  I also assigned the drive letters so it would mimic MS-DOS letters.  I guess I was bored that day.

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7 Responses to NaBloPoMo – DEC Micro PDP-11/73

  1. jaypo says:

    Double post, LordK. So the DOS is pretend?? Oh well, it's a nostalgic touch.

  2. Lord Kalvan says:

    I accidentally posted twice. RT-11 actually predates DOS by almost a decade. So its not really pretend. I just had it mimic the DOS drive letters instead of DU1: and DU1: for the floppy drives. Beside Gates (MS-DOS) stole from Kildall (CP/M) who copied from DEC. Some of the commands are the same such as DIR and TYPE.

  3. Lord Kalvan says:

    The pictures are of the actual output of the operating system. The system outputs serially to a terminal instead of a monitor. The assign command lets one rename devices.

  4. jaypo says:

    Well, that explains it! Smartypants. ;-P

  5. dewitte says:

    I think one of the first online systems I used was a PDP 11. It had something after it, like PDP 11/785, but then there was a VAX something that we used right after. My first email address was or something like that which was awesome at the time because whenever I logged in and someone did a "who" they'd say "Hey, there is a tomato on the system."Ah, good times, good times… That was 1983.

  6. Lord Kalvan says:

    It could have been an VAX 11/785 in PDP 11 compatibility mode. The 11 series VAXen could run RSX in this mode with many of the PDP11 instructions directly supported (IIRC). I also believe they were marketed as PDP11/7xx occasionally especially with the RSX supporting software installed. I had found a reference to that but can't find it again.

  7. dewitte says:

    Sadly, I have a complete memory failure on the two – VAX 11/785 sounds right as does PDP 11/780 but then PDP 10 sounds good too. Maybe I'll group them both together for my post and label it as correct to the best of my knowledge.

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