Modifying microcode

[Robert Armstrong]

> Tony Duell <ard.p850ug1 at gmail.com> wrote:
>Incidentally, did DEC ever release any details (flowcharts, source listings,
>etc) of the 11/730 microcode? And what about the control PROMs for the
>memory system. The technical manual implies there was a listing of those,
>but I've never found it.

  I thought that DEC had a whole microcode development suite for the 730 to support customer written extensions to the microcode, but I've never seen it nor any documentation for it.  If such a thing did exist then I seriously doubt anybody ever bought it.  The 730 was never a super popular machine to start with, and the market for a customized version would have been very small.

  I've heard a persistent rumor over the years that the WPS/8 and PDP-8 software group at DEC had modified the 730's microcode to support a PDP-8 emulation of some kind, and that they used that internally for development 'cause it was faster than a real -8.  I've not idea if that's true, but it would be cool if they did.  And no, I'm not talking about PDP-11 compatibility mode - even the stock 730 had that (all the 7xx VAXes did, I believe).

  Certainly if you had the right tools and the right knowledge, it would have been easy to modify and replace the 730's microcode with something of your own.  Just copy the binary images to the console tape and reboot.

Bob