[TUHS] A PDP-10 used for UNIX just after the PDP-7?

[Phil Budne via TUHS]

Thalia Archibald wrote:
> On Jan 15, 2026, at 23:57, Ken Thompson wrote:
> > after the pdp-7, unix was ported to more
> > stock pdp-9 and pdp15 (both pdp7 upgrades)
> > 
> > no pdp-10 at bell labs.
> So the "PDP-10" that Mahoney refers to is the PDP-11 with KS-1 memory
> management? Seems like a strange machine.

https://gunkies.org/wiki/KS11_Memory_Protection_and_Relocation_option

describes an MMU much like the KA10 (first PDP-10 CPU): Two sets of
base and limit registers (highseg and lowseg).  I think the second set
of registers was an option on the KA (*).  The PDP-10 was a follow-on
for the PDP-6, which only had one base/limit pair.

(*) Way WAY too much info for the TUHS list:

The PDP-6, DEC's first machine larger than 18 bits had been regarded
as an overreach for the then small company (only 23 were sold).  Among
other things it used large circuit boards that had to be soldered in,
and the largest (core) memory box sold was 16K.  One customer who
wanted to run time sharing using only DEC memories returned the system
because it was too flaky, but shops that bought larger memory boxes
from 3rd parties had no problems.

To get buy-in to making a follow-on to the '6, they went to ridiculous
ends to make it possible to price the base system around $100,000 (the
bare PDP-6 CPU listed at $176K) including making the following
options:

KE10	KA10 byte instruction option ("extended order code")
KM10	KA10 16 Word 0.21 microsecond fast memory (ACs) option
KP10	KA10 power fail/restart option [I/O Bus & 7 level PI?]
KT10	KA10 single protection/relocation reg [never sold]
KT10A	KA10 dual protection/relocation regs

Without "fast ACs", the registers (visible as the first 16 addresses)
used external core (was also an option on the PDP-6).