Modifying microcode

[Paul Koning]

> On Jun 2, 2018, at 2:08 PM, Robert Armstrong via cctalk <cctalk at classiccmp.org> wrote:
> 
>> 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.

Considering that the 730 was a 2901 based machine, and 2901s were widely used, presumably the tools were not a problem around DEC.  Perhaps they tweaked the UDA50 microcode toolchain?

>  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).

The PDP-8 emulation used for internal PDP-8 software development was on an 11/60 running RSTS/E, I remember that system in the lab in DEC Merrimack (MKO1-1).  I would imagine it could have been done on a 730 also but chances are the 11/60 was a whole lot faster.

	paul