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

[John Levine via TUHS]

It appears that Clem Cole via TUHS <clemc at ccc.com> said:
>ITS was moved from the PDP-6 to a couple of different PDP-10
>implementations. And TOPS-10 evolved from the DEC PDP-6 monitor. BBN wrote
>Tenex for a modified PDP-10, but they had certainly learned many lessons
>from their (modified) PDP-6  and PDP-1 systems

That's not much of a port.  The program differences between the PDP-6
and the original KA10 were tiny.  Same data formats, same instruction
set, even pretty much the same I/O architecture.

Going to the KI10 which had paged virtual memory was more of a change.
The KL10/20 which had expanded memory addressing and a new I/O architecture
with a PDP-11 front end was an even bigger change.

R's,
John



>
>On Mon, Mar 23, 2026 at 9:15 PM George Michaelson via TUHS <tuhs at tuhs.org>
>wrote:
>
>> EMAS was ported from the ICL 1900 to the 2900 at Edinburgh Uni across this
>> time.  In like sense TOPS-10 was ported from the 10 to the 20 but that was
>> at worst a marginal conversion. Obviously the entire suite of DEC RSTS type
>> operating systems were cross ported to the variants of the PDP11 on an
>> as-emerged basis, but I suspect like tops10/20 that was hardly a "port" in
>> any real sense ...