PDP-11/34 CPU PROMS

[Sytse van Slooten]

>>> On Tue, Feb 8, 2022 at 7:04 PM Warner Losh <imp at bsdimp.com> wrote:
> 
>>> I found
>>> https://deramp.com/downloads/mfe_archive/011-Digital%20Equipment%20Corporation/08%20PDP-11/01%20PDP-1104-1134/05%20PDP-1104-1134%20Microcode/
>>> which has the source code...
>>> 
>>> But I couldn't find the tools to use these files to create microcode
>>> images.
> 
> Actually, the "m8266_ucode.v.txt" there seems to actually be the program that
> produced the symbolic dump (which is also available at:
> 
>  http://www.bitsavers.org/pdf/dec/pdp11/1134/m8266_ucode.out.txt)
> 
> It looks like the program is in VHDL or something like that, but it doesn't
> seem to have the actual microcode (was it stored/defined in another VHDL
> file?); that raises the question of where the actual microcode that it was
> dumping was.

It's Verilog (the 'other' hardware language besides VHDL), and indeed the rom images are in other files/modules - in some kind of straight binary format, I'd guess.

I'm properly intrigued why someone would choose to do this - which seems to be mostly listing the microcode in a readable format - in Verilog. Unless of course it would be with a long term goal of using that microcode in an emulator that is sufficiently like a 'real' 11/34 to run it unchanged. I wonder if that is the case, and what became of the project - since the files are from 2014, it's probably safe to assume it got stuck somewhere along the way.

Somewhere way down on my list of things to explore is something similar but then for the 11/70 - to make a vhdl version that is microcode compatible with the original, unlike the current pdp2011 that's 'only' functionally compatible. And this is about exactly the same way I would start - except I don't have the '70 rom images yet... If anyone has them and is willing to share, drop me a note ;-)

Cheers
Sytse