Re: [pups] PDP-9?

Dave Horsfall: AFAIK, Unix never ran on the 11/20 (no MM unit); did you mean a DEC-20? I don't know if it was called an 11/20 at the time (I seem to recall some model-number upheaval in the early days of the -11), but the first PDP-11 UNIX system was certainly one without memory management: By the beginning of 1970, PDP-7 UNIX was a going concern ... In early 1970 we proposed acquisition of a PDP-11, which had just been introduced by Digital ... to create a system specifically designed for editing and formatting text, what might today be called a `word-processing system.' ... During the last half of 1971, we supported three typists from the Patent Department, who spent the day busily typing, editing, and formatting patent applications, and meanwhile tried to carry on our own work. UNIX has a reputation for supplying interesting services on modest hardware, and this period may mark a high point in the benefit/equipment ratio; on a machine with no memory protection and a single 0.5-MB disk, every test of a new program required care and boldness, because it could easily crash the system, and every few hours' work by the typists meant pushing out more information onto DECtape, because of the very small disk. The experiment was trying but successful. Not only did the Patent Department adopt UNIX, and thus become the first of many groups at the Laboratories to ratify our work, but we achieved sufficient credibility to convince our own management to acquire one of the first PDP-11/45 systems made. Dennis M. Ritchie, Evolution of the UNIX Time-Sharing System; AT&T Bell Labs Technical Journal, Vol. 63 No. 8 Part 2, October 1984. Maybe Dennis will chime in with further memories. Certainly there's nothing odd about UNIX running without memory protection, though, especially in that era. The PDP-7 had none. The trick was that every context switch was also a swap. The scheme was revived in the late 1970s for the early, no-memory-map versions of the LSI-11 (called LSX and later Mini-UNIX; paper by Lycklama et al in the 1978 all-UNIX BLTJ, I believe). I suppose next some whippersnapper will express disbelief that UNIX could have run on a system with no Ethernet interface. You mean there was life before 10BaseT, spam, and pornographic web sites? (Not, to be fair, that Dave Horsfall is a whippersnapper.) Norman Wilson Toronto ON (Still on the shelf, but crawling toward the edge)