[TUHS] [TUHS} PDP-11, Unix, octal?

Angelo Papenhoff aap at papnet.eu
Wed Jan 18 16:53:51 AEST 2017


On 17/01/17, Dan Cross wrote:
> A question about 36 bit machines....
> 
> In some of the historical accounts I've read, it seems that before the
> PDP-11 a pitch was made for a PDP-10 to support the then-nascent Unix
> efforts. This was shot down by labs management and sometime later the
> PDP-11 arrived and within a decade or so the question of byte width was the
> creatively settled for general purpose machines.
> 
> The question then is twofold: why a PDP-10 in the early 70s (instead of,
> say, a 360 or something) and why later the aversion to word-oriented
> machines? The PDP-7 was of course word oriented.
> 
> I imagine answers have to do with cost/performance for the former and with
> regard to the latter, a) the question was largely settled by the middle of
> the decade, and b) by then Unix had evolved so that a port was considered
> rather different than a rewrite.  But I'd love to hear from some of the
> players involved.

Doesn't exactly answer your question, but from the "Oral History of Ken
Thompson":

Q: As I recall this - once upon a time weren't you trying to get a
PDP-10 or something like that for the lab?

Ken Thompson: Yes, we were arguing that the Multi[cs] machine should be
replaced with a PDP-10. And there was such a huge backlash from
Multi[cs] that it was pretty soundly turned down. It was probably a good
idea, the -10 is a kind of trashy machine with 36 bits - the future just
left it behind.


"the -10 is a kind of trashy machine with 36 bit"
I'm not sure whether I can still like UNIX now :( I hope this is the bad
(?) experience with Multics on the GE-645 speaking.

"the future just left it behind"
More like DEC didn't want internal competition with the VAX.

aap


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