winter's computers
found, loved, and nurtured for spring
my ugly geek secret

Tuesday, June 12, 2007



  • DEC PDP-11/44
  • 1979
  • DEC PDP-11/44
  • 256 KB, 512 KB, 768 KB, or 1MB (don't remember which)
  • Data General 6500A serial console (VT52 compatible terminal)
  • DEC RL01 5.2 MB disk cartridge subsystem
  • Plessey PM-DDA11/B 5 MB dual fixed / removable cartridge subsystem
  • none installed
Operating Systems
  • RT-11
  • RSTS/E
  • Unix
  • CDA MSP-3000 Array Processor
I used one of these in college for a low-level programming course. Its assembly language is a thing of beauty. The CPU is several boards inside the second unit from the top.

The terminal was a later addition. Previously I just used a terminal emulator on one of my DOS PCs, which turned out handy when — while inspecting the CPU — I snapped a pin off the boot rom. Fortunately I got the short boot code from somewhere (one of the thousand manuals that came with it, I think) and wrote a little BASIC program on the DOS PC that would feed the boot code to grimlock's console then boot it. It worked like a charm.

I had grimlock almost booting off a cartridge in the RL01 (top unit), but after throwing a few characters on the console saying it was booting Unix it just hanged. I don't know if the problem is the RL01 or the cartridge, but I have almost a dozen others that I haven't tried yet.

Some of them are for the Plessey drive (third unit from the top), which is a weird beast that has a removable cartridge portion and a non-removable cartridge sealed inside it. The entire unit pretends to be two RK05Js.

I haven't tried to get it to work yet, nor the array processor (bottom unit), which is like the numerical coprocessor chip on pre-Pentium PCs. One interesting feature of the array processor is that in 1979 it implemented instruction pipelining, a feature that Intel added to the '486 ten years later.

I've got a box full of expansion cards, too. One might be a network card, but right now this thing has no network capability.

I haven't turned grimlock on since I lived in Port Moody 15 years ago. The CPU by itself sounds like a jet plane taking off. In Keremeos I was always afraid the street lights would dim if I started it up.

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