8

The PDP-1x is a Digital Equipment Corporation PDP-1 computer modified to support both ones and twos complement arithmetic, and to include a memory management unit. It ran a locally developed operating system with specific facilities to represent virtualized devices and inter-process communications. The top-level element was called a "Sphere". It contained resources (called capabilities) and execution elements. I believe the execution elements were called "processes".

There was a manual for the OS named "INSTR5 ALL". I would like to read more about the OS to see if I was just a youngster amazed by something I was unfamiliar with, or if this operating system was unique and worthy of re-examination today.

Where could I find documentation of the PDP-1x Operating System?

  • 1
    Is this doc related in any way? Probably not, but I thought it wouldn't hurt to post it just in case. – another-dave Mar 20 '19 at 22:10
  • This looks to predate the changes which turned the pdp1 into the pdp1x. Good for history, and I will read it. Thank you! – cmm Mar 20 '19 at 23:12
  • I'm still hoping to find the documentation for the PDP-1x OS. – cmm Jul 17 '19 at 1:05
  • I'm very interested in this, because the MIT Logo group SITS operating system for their PDP-11/45 also has capabilities and the concept of a "sphere". As far as I can see, they mean exactly the same thing. – Lars Brinkhoff Jan 23 at 6:41
9

I believe this is the best place for PDP-1X documentation:

http://bitsavers.trailing-edge.com/pdf/mit/rle_pdp1/
(Linking to a mirror because the main bitsavers.org is offline for the moment.)

The 1975 memo PDP35, part 5A documents spheres and capabilities:

A virtual memory space, any virtual processors (processes) that might be executing inside that memory space, plus the list of associated resources (C-list) comprise a sphere.

Interestingly, these exact concepts - spheres, processes, capabilities - were carried forward to the MIT Logo group timesharing system SITS.

  • Lars, this is exactly what I couldn't find. Thank you. -- Carl – cmm Jan 23 at 11:01

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.