PDP-11/05 microcode dump?

Josh Dersch derschjo at gmail.com
Fri May 6 11:09:07 CDT 2016

On 5/6/16 6:26 AM, Noel Chiappa wrote:
>      > From: Mattis Lind
>      > Has anyone dumped the microcode of the PDP-11/05?
>      > ...
>      > When tracing the microprogram flow it looks very suspicious. Comparing
>      > the same sequence with a better working pair reveal a few differences.
>      > All these can be narrowed down to one single PROM chip.
> Josh had an 11/05 that had a uROM fail, and he had to blow a new one (IIRC he
> sent in a report, it's in the list archive). I'm not sure if it's the same one
> as the one you need, but if his post doesn't give the chip ID, no doubt he can
> let us know.
I had two uCode ROMs fail, it was just that fun.  Unfortunately they 
were at E114 and E102 (A11A2 and A20A2), not E103 so my transcriptions 
aren't going to help.

I've put them up at http://yahozna.dyndns.org/scratch/pdp1105/ucode if 
anyone happens to need them, this includes the raw binary as well as the 
transcription I did.  I had my wife double-check my work (she's very 
patient with me) and the PROMs seem to work fine (all diags pass) so I'm 
pretty sure they're correct.

Note that the order of the data in the A11A2 PROM is reversed from the 
engineering drawing transcription; the address lines to that PROM are 
active low (discovered this the hard way.)

- Josh

>      > There are microcode listings in the manual but they need to be treated
>      > to get into a dump.
> Which is exactly what Josh did.
> Speaking of which, is there any chance we can get those machine-readable
> listings online? I can host them with my other DEC material, and I can also
> put them in the Computer History wiki.
> 	Noel

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