[TUHS] PDP-7 Unix Progress

Greg 'groggy' Lehey grog at lemis.com
Wed May 4 12:42:39 AEST 2016

On Wednesday,  4 May 2016 at 12:12:40 +1000, Warren Toomey wrote:
> On Wed, May 04, 2016 at 12:44:15AM +0300, Diomidis Spinellis wrote:
>> This would have found any code from the PDP-7 Unix that appeared in the
>> First Edition.  (I was hoping that some PDP-7 instruction sequences might be
>> the same in PDP-11.)
>> Unsurprisingly, nothing came out.
> No, the instruction set is completely different. The PDP-11 ISA is a
> paradise compared to the spartan PDP-7 ISA.

In case you're interested, I've located a reference manual at

The instruction set is very reminiscent of the PDP-8, including the
"operate" class "microcodding" instructions (starting with 7) and
autoindexing via indirect access to locations 10 to 17.  Even the
mnemonics and the assembler syntax are very similar to the -8.

Certainly the PDP-11 is an improvement, but there's something
nostalgic about the -7 instruction set.

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