From firstname.lastname@example.org Thu Jan 25 19:15:51 1990
Subject: DEC's PDP family tree
From: email@example.com (Bob Devine)
Date: 22 Jan 90 23:05:44 GMT
Organization: Digital Equipment Corp. - Colorado Springs, CO.
In the beginning was the PDP-1 ...
PDP-1 = first commercial interactive computer; late 1960; had 18 bits
PDP-2 = a PDP-1 with another mem board
PDP-3 = A DEC customer (Scientific Engineering Institute, Waltham, Massachusetts) built a PDP-3 in 1960. It finally was given to M.I.T., and eventually wound up in Oregon (1974).
PDP-4 = a modified PDP-1
PDP-5 = "first minicomputer" introduced in early 1963
PDP-6 = a 36-bit machine; came out in late 1964
PDP-7 = a modified PDP-4
PDP-8 = successfully mass-produced follow-on to PDP-5; 1965
PDP-9 = a modified version of the PDP-7 (it started life as a PDP-7/X). Its main advance over the PDP-7 was in the memory design.
PDP-10 = follow-on to PDP-6; 1967
PDP-11 = an entire family of these 16-bitters was made; 1970
PDP-12 = sort of a PDP-8 merged with the LINC machine
PDP-13 = no such machine!
PDP-14 = some sort of industrial computer
PDP-15 = a whole family of computers (the PDP-15/10, /20, /30, /35, /40, /50, and /76). One of the first DEC computers to use ICs extensively. First PDP-15 shipped in February 1970.
PDP-16 = some sort of industrial computer
The family tree goes something like this:
PDP-1 --> PDP-4 --> PDP-7 --> PDP-9 --> PDP-15
PDP-5 --> PDP-8 --> PDP-12
PDP-6 --> PDP-10 --> DECsystem-10 --> DECsystem-20
PDP-11 --> VAX
A good overview of the DEC family of computers can be found in the book "Computer Engineering - A DEC view of hardware systems design", by C. Gordon Bell, J. Craig Mudge, and John E. McNamara. It is published by Digital Press, ISBN 0-932376-00-2.
From mmt@client1.DRETOR.UUCP Thu Jan 25 19:15:20 1990
Subject: PDP-9T in DEC's heritage
From: mmt@client1.DRETOR.UUCP (Martin Taylor)
Date: 23 Jan 90 00:18:51 GMT
Reply-To: firstname.lastname@example.org (Martin Taylor)
Organization: D.C.I.E.M., Toronto, Canada
Summary: DEC's first memory mapped time-sharing machine
Brian Stuart gave a nice chart of the DEC family of computers:
Year 18-bitters 12-bitters 16-bitters 36-bitters 1960 PDP-1 ------------------------------------------------------- | \ 1962 PDP-4 <--- LINC -------- \ 1963 | PDP-5 \ \ | 1964 PDP-7 | \ \ PDP-6 1965 | PDP-8 --\ | \ | 1966 | PDP-8/S LINC-8 | | 1967 | | | | KA10 1968 PDP-9 PDP-8/I,L | | | 1969 | | PDP-12 | | 1970 PDP-15 | PDP-14 PDP-11(/20) | 1971 | PDP-8/E / | \ | 1972 PDP-15/76 PDP-8/M - PDP-11/05 | PDP-11/45 -- KI10 1973 | / | PDP-11/40 | \ | | / | | | \ | 1975 PDP-8/A PDP-11/03 PDP-11/04 | | PDP-11/70 KL10 1976 | PDP-11/34 | PDP-11/55 | KL20 1977 VT78 | PDP-11/60 | 1978 PDP-11/34C VAX-11/780
but at least one is missing: the PDP-9T of 1967-8. This was, as far as I know, DEC's first memory mapping computer designed for real-time time-shared experiment control. (I know the PDP-1 was time-shared, after a fashion, but the 9T had proper separation of all address spaces, round-robin scheduling, and so forth).
The story is more or less as follows: DCIEM had been looking for a shared experiment controller, and I was considering whether we could modify a PDP-7 along the lines of the SDS-940 at Berkeley(? where Butler lampson was, if not Berkeley). DEC's Canadian salesman, Sy Lyle, took my proposal to Maynard, and came back with stories of this wonderful new super-PDP-7 on which we might try the idea if we could persuade the project manager, John Jones. So off I went to Maynard, on the way passing by Harvard Psych Department, where they were in the planning stage of buying 4 IBM 1800s for experiment control. There I got Dan Forsythe and Don Norman interested, and we all went to see John Jones in the old mill in Maynard. After a few minutes of my presentation, he asked us to wait while he called in his Chief Engineer, Larry Seligman, who listened for about 20 minutes. Jones asked him what he thought, and he said "I like it," so Jones said "We'll do it."
That's the kind of company I like.
So what happened? Harvard and DCIEM both bought one, but San Diego did not, and neither did anyone else. The Harvard and DCIEM machines were developed in parallel with the normal PDP-9, leapfrogging each other in the development of their time-sharing hardware. Seligman devised a neat instruction-mapping device that allowed individual users to have their own privileged instruction sets and enabled them to exercise direct control over their I/O devices (wild, for a fully protected real-time time-sharing machine; I often wonder why it was not ported to the PDP-11 along with the memory mapping scheme).
Unfortunately, in the middle of the PDP-9 development, Seligman went back to university, leaving the PDP-9 in the hands of a less imaginative Chief Engineer. The PDP-9 that Seligman designed was later built, and called the PDP-15 (at least many of the characteristics of the PDP-15 were those Seligman had specified for the PDP-9 but did not appear in the 9). As a result, the actual PDP-9T was not the clean machine that it should have been. DEC never produced any software for the 9T, and as far as I can gather, never tried to sell any other than the two development machines. But those two ran experimental psychology labs for over a decade, quite successfully.
The PDP-9 had an address space of 32K 18-bit words, but the mapped machine allowed 256K. The virtual machine seen by the users was identical to a normal PDP-9 except for the 256 extra instructions provided by Seligman's I/O mapping trick, some of which did virtual DMA for non-DMA devices, provided timing services, and the like (for real-time experiments). On the normal PDP-9, the user had to use a minimum of 8K because of the ADSS monitor, but on the 9T, the user could be as small as 2K, which was plenty for many experiments. Users were guaranteed a response to an interrupt within 10 msec, and usually got it within 2 msec (all in-core, there was no swapping), with as many as 10 real-time users. Scheduling was a round-robin with 1 msec frames.
The PDP-9T inspired two sharp characters from Harvard, Rob Strom and Bob Walton, to produce both software and theoretical studies of time sharing. Walton, in particular, devised a theory of guaranteed real-time time-sharing that was not put into practice (as far as I know) until perhaps 10 years later on the PDP-11/34 and 11/70, with our (DCIEM and Andyne Computing Ltd.) MASCOT modifications to the UNIX kernel. The software development for the machine was a joint project of Harvard Psych Department and DCIEM.
Fun Days, with a Fun Machine. I wish DEC were like that now!
From "The PDP-11 FAQ" ftp://ftp.update.uu.se/pub/pdp11/faq
MODEL DATE PRICE BITS COMMENTS ===== ==== ======== ==== ===== PDP-1 1960 $120,000 18 DEC's first computer PDP-2 NA 24 Never built? PDP-3 36 One was built by a customer, none by DEC. PDP-4 1962 18 Predecessor of the PDP-7. PDP-5 1963 $27,000 12 The ancestor of the PDP-8. PDP-6 1964 $120,000 36 A big computer; 23 built, most for MIT. PDP-7 1965 ~$60,000 18 Widely used for real-time control. PDP-8 1965 $18,500 12 The smallest and least expensive PDP. PDP-9 1966 $35,000 18 An upgrade of the PDP-7. PDP-10 1967 $186,500 36 A PDP-6 successor, great for timesharing. PDP-11 1970 $10,800 16 DEC's first and only 16 bit computer. PDP-12 1969 $27,900 12 A PDP-8 relative. PDP-13 NA Bad luck, there was no such machine. PDP-14 A ROM-based programmable controller. PDP-15 1970 $16,500 18 A TTL upgrade of the PDP-9. PDP-16 1972 $.8-$4,000 NA 8/16 A register-transfer module system.
Since then, the PDP-11 had 16 to 22 implementations, depending on how you count them, many with variants. The following attempts to briefly track the evolution and progression.
In 1969 the -11 family was projected as follows:
Model CPU Comments
11/20 KA11 Origin of the species 1x performance. 11/10 - .7 of the 11/20, technologically cost reduced 11/20 in MOS. [This obviously became the 11/05, 11/10] 11/30 KA11 [Seems to have been the same as an 11/20 packaged with a little more memory, etc. I believe this is what eventually became the 11/20 that actually shipped] 11/40 KB11 2x performance. 11/45 KB11 2x performance. [Seems to have been intended to be an 11/40 with MMU. [Looks like this became the 11/40 that eventually shipped.] 11/50 KC11 2x performance. Hardware floating point 32 bit processor. [I believe the 32 bit refers to the FPU!] 11/55 KC11 2x performance. With MMU. [It looks like the 11/50 plus 11/55 became the eventual 11/45] 11/65 KD11 4x performance. 32 bit separate memory bus, 32 bit processor.
PDP-11 Operating Systems
DOS/BATCH RSTS, RSTS/E Resource Sharing/Time Sharing. General purpose Time sharing system. CAPS-11 Cassette Based Programme development System. MUMPS-11 Massachusetts General Hospital Multi-User Multi-Processing System. A language, an operating system and a DBMS all in one. RT11 Real Time. Foreground/Background or Single Job operating system. TSX11 Multiuser enhancements to RT11 (third-party). RSX11 Resource Sharing eXecutive. Multiprogramming system. RSX11/M Small to moderate-sized real-time multiprogramming system. RSX11/M+ Extended RSX-11/M. RSX11/S Execute-only real-time multiprogramming system. RSX11/D Large real-time multiprogramming system. RSX-11B/C, Micro/RSX IAS Interactive Application System. Multi-purpose multiprogramming system. TRAX Transaction Processing system. Unix (tm) Much/most of Unix was developed on PDP-11s. MERTS (MERTSS?) A virtual operating system that could run Unix as a process. Several machines at BTL ran MERTS. CTS-300 There's some confusion as to whether this is just a re-packaged version of RT-11, or a time-sharing system layered on top of RT-11. CTS-500 There's some confusion as to whether this is just a re-packaged version of RSTS, or a time-sharing system layered on top of RSTS. TSX Time-sharing system layered on top of RT-11. HT-11 Heathkit's hacked version of RT-11, wouldn't run on a "real" PDP-11. Ultrix Digital's implementation/port of BSD UNIX. Venix A third-party implementation/port of UNIX.
Return to PDP-11 History pdphistory.html
Revised September 01, 2007 02:34:56 AM.
Copyright © 2007 William Bader.