[TUHS] porting to different systems, Bootstrapping UNIX - how was it done

[John R Levine via TUHS]

On Fri, 27 Mar 2026, arnold at skeeve.com wrote:
> If I recall correctly, the labs port was to an Interdata 8/32.

Quite possibly.  Programming for the 7/32 and 8/32 were nearly the same.

R's,
John

> John Levine via TUHS <tuhs at tuhs.org> wrote:
>
>> According to Noel Chiappa via TUHS <jnc at mercury.lcs.mit.edu>:
>>> 2 - Move a set of existing software from one type of machine to another. (A
>>> much more common event, now that we have portable software. Speaking of
>>> portable software, I'm still amazed that this, which became one of Unix's
>>> most important attributes, and a major driver in its spread, after V7, does
>>> not appear to have been really thought about before V6/V7 was ported to
>>> several other architectures.)
>>
>> I don't think it occurred to anyone until that that it would even make sense to
>> move an operating system from one kind of computer to another. Historically,
>> architectures were different, data formats were different, I/O architecture was
>> different, and everything was written in assembler or maybe a language tied to
>> the system like Burroughs Algol.
>>
>> By a decade after S/360 came out, computer architectures had all converged on
>> 8-bit byte addressable two's complement designs with multiple registers. (Older
>> machines like the PDP-10 weren't dead yet but it was just a matter of time.)
>> Then Unix came along, written mostly in C which was highly portable to those
>> 8-bit byte addressable machines. The group at the Labs allegedly picked the
>> Perkin Elmer 7/32 because it was as different as possible from the PDP-11, but
>> it wasn't all that different. It was 32 bits but the data formats were the same
>> (give or take a few details of floating point), addressing and memory protection
>> were similar to the PDP-11, and it had terminals and disks.
>>
>> Wollongong and the Labs separately did 7/32 ports, both probably observing
>> that if they retargeted the C compiler to the 7/32 and recompiled the PDP-11
>> C code, they were about 80% of the way there, so the rest of the work was
>> a manageable project.