Subject: Let's update this list!

From: [email-masked] (Charles Lasner)
Date: 20 Mar 1994 02:31:55 GMT

I was going through the back posts of pdp8-lovers and found Mark
Crispin's "authoritative" list of PDP's.  In light of Doug Jones' FAQ's,
etc. it would seem interesting to comment on it today!

Date: Thu,  8 Jun 89 00:09:28 EDT
From: "Robert E. Seastrom" <[email-masked]>
Subject:  What's a PDP-x ??
To: [email-masked]

If you folks have already seen this, please disregard it.  If
you haven't, keep it handy - it could come in handy some day.
[Is today that day?  - cjl]

                      ---Rob

PS: In case you didn't know (I didn't until 2 years ago), PDP
stands for Programmed Data Processor...

Date: Wednesday, 20 August 1986  03:42-EDT
From: Mark Crispin <[email-masked]>
To:   [email-masked], [email-masked]
Re:   DEC's PDP's

     A number of people have requested my list of all the DEC PDP's,
so I thought I'd bore you all with it.

     The PDP-1 was an 18 bit machine.  It was DEC's first computer,
and some of the first timesharing systems were designed for it.  It's
also unique in being one's complement; all later DEC computers were
two's complement.  Some machines, such as one of MIT's PDP-1s, were in
operation until the late '70s.
[The LINC portion of the LINC-8 and PDP-12 are one's complement! - cjl]

     The PDP-2 was a designation reserved for a 24 bit machine, but as
far as I can tell it was never even designed and definitely none were
ever built.

     The PDP-3 was a 36 bit machine that was designed but never built
by DEC.  However, Scientific Engineering Institute built one in 1960.

     The PDP-4 was an 18 bit machine that was intended to be a
cheaper, slower alternative to the PDP-1.  It was so slow that it
didn't sell well, although it was interesting for its
auto-incrementing memory registers.  It was not program-compatible
with the PDP-1, but its instruction set was the basis of DEC's future
18 bit computers.

     The PDP-5 was a 12 bit machine designed to be a small laboratory
system.  It used many of the ideas in the LINC (Laboratory Instruction
Computer, designed by Lincoln Labs at MIT, some of which were built by
DEC).

     The PDP-6 was a 36 bit machine and the first machine to implement
the most wonderful computer architecture known to man. [! - cjl]
  It was rather
expensive and difficult to maintain, and not many were sold.  As a
result, DEC cancelled 36 bit computers for what was to be the first of
many times.

     The PDP-7 was an 18 bit machine and the sucessor to the PDP-4.
It was a major price/performance win over the PDP-4 and the first DEC
computer to use wire-wrapping.

     The PDP-8 was a 12 bit machine and the sucessor to the PDP-8. [I 
assume he means -5! - cjl] It
basically defined the term "minicomputer", and went through several
incarnations.  The original PDP-8 was followed by the extremely slow
PDP-8/S (as bad as the PDP-4 was to the PDP-1, but at least the /S was
program-compatible). [I wouldn't be too sure about that! - cjl]  DEC 
recouped with the PDP-8/I (using MSI
integrated circuits) and the smaller PDP-8/L, and somewhat later came
out with the "Omnibus 8" machines -- the PDP-8/E, the PDP-8/F (a
half-sized version of the PDP-8/E), the PDP-8/M (an OEM version of the
PDP-8/F), and the final machine, the single board PDP-8/A.  The
PDP-8/A still exists after a fashion as a current DEC product.

     The PDP-9 was an 18 bit machine and the sucessor to the PDP-7.
It had a faster memory than the PDP-7 and was the first
microprogrammed DEC computer.  Modulo a 300 wire(!) ECO required in
the first machines, the PDP-9 was a reliable machine and some are
still in operation today.  There was a short-lived PDP-9/L.
[Can someone explain what he means by "microprogrammed" ? -cjl]

     The PDP-10 was a 36 bit machine and the sucessor to the PDP-6.
It is especially noted for its software, which represents the pinnacle
of DEC software engineering and has never been equalled.  The first
KA10, largely installed in universities, created a whole generation of
timesharing hackers.  The follow-on KI10, with paging and using IC's
instead of discrete components but otherwise unexciting, mostly was
sold to commercial organizations.  The KL10 went through several
incarnations and is today the most representative of this marvelous
machine.  The KS10 was a small, low-speed (approximately KA10
performance) processor which was DEC's last successful implementation
of this architecture.

     The PDP-11 was a 16-bit machine that went through more
implementations and operating systems than can be counted.  Presently
it superceded the less powerful PDP-8 as the representative
minicomputer. [Some of us might take exception to this statement! - cjl]
 While the PDP-11 used octal, it was in its deep heart
of hearts a hexidecimal machine, and the first indicator of the
creeping IBMification of DEC that took full fruit in the VAX.  [I can
hear the flames now...]  Rather than fight it the customers loved it;
more PDP-11's have been sold than any other DEC computer (possibly
more than all the others combined).

     The PDP-12 was a 12 bit machine and the sucessor to the PDP-8.
It combined a LINC and a PDP-8 type processor in the same box and
basically was a new model of the LINC-8 which was the same thing.

     No PDP-13 was ever designed or built.  Even DEC gets
superstitious.

     The PDP-14 was a 12 bit machine with a 1 bit register.  It was
used as a process control engine in applications that were felt to be
too rugged for a PDP-8, and basically replaced a set of relays.  Later
DEC made PDP-8's suitable for this sort of thing, but it didn't stop
them from the ultimate silliness of building a PDP-14 that used a
PDP-8 as its console processor! [I remember something about a 
KL8-JA-oriented diagnostic that was for checking out somesuch 
configuration! - cjl]

     The PDP-15 was an 18 bit machine and the final one of this design
built by DEC.  More PDP-15's were built and sold than any of the
others, [I assume he means other 18-bit DEC machines! - cjl] and it went 
through several incarnations including some 
which used a PDP-11 as a front end.  Apparently the cancellation of the
PDP-15 came as a great surprise to the "Tiger Team" who worked on it,
although considering its general ungainliness compared to comparable
performance PDP-11's it wasn't surprising.  In many ways the PDP-15
died for the same reason the PDP-10 did. [I for one want this elaborated 
on! - cjl]

     The PDP-16 was a "roll your own" 16 bit machine based on various
"building blocks".  Every PDP-16 was essentially custom-designed by
the customer.  It got a fair amount of attention when it was announced
but evidentally didn't sell very well.

     There was no PDP-17 or any other designator.  DEC apparently
decided that "PDP" had a perjorative ring to it.

_______

Any other comments out there in our PDP-8 Peanut Gallery?

cjl

---

From: [email-masked]
Date: 20 Mar 94 20:46:54 MDT

> [Can someone explain what he means by "microprogrammed" ? -cjl]

I presume he means that the machine code is interpreted by a controller
driven by microcode.

-- 
----------------+------------------------------------------------------
Roger Ivie      | Don't think of it as a 'new' computer, think of it as
[email-masked] |     'obsolete-ready'

---

From: [email-masked] (Charles Lasner)
Date: 21 Mar 1994 15:07:23 GMT

>I presume he means that the machine code is interpreted by a controller

Perhaps someone who really knows the answer can respond!  I agree that's
what it ought to be, but nothing I've ever heard about the 7/9/15 series
would tend to support it.

On the contrary, could this perhaps be a mangled reference to the way the
PDP-8 and the 7/9/15 family handle micro-programmed operates?

On the -8, there are distinct groups of operates; you can only combine
operations within a group.  On the 7/9/15, just about anything goes.
Although I don't think the -8 is really lacking much by its
restriction.  But I suppose that there are those that would appreciate
instructions like:

	SPA SNA CLL CML HLT

Additionally, there is the issue of the fact that all operations only
take one cycle regardless of the number of operations present, etc.

So, anyone out there that can tell us what's the difference between the
implementation of some form of -8 and the 7/9/15 series other than the
obvious (word-length, DAC instead of DCA, etc.).

cjl

---

From: [email-masked] (Douglas W. Jones,201H MLH,3193350740,3193382879)
Date: 21 Mar 1994 18:32:24 GMT

>From article <[email-masked]>,
by [email-masked] (Charles Lasner):
> Crispin's "authoritative" list of PDP's.

	A fun find.  Thanks for reposting it!

>      The PDP-1 was an 18 bit machine...  It's also unique in being
> one's complement; all later DEC computers were two's complement.  ...
And limited support for one's complement was preserved in the remaining
18 bit machines, up to the very end.

> didn't sell well, ...
Dec used PDP-4 machines to control their first generation automatic
wire-wrap equipment and possibly for other factory automation functions.

> but evidentally didn't sell very well.
I was a user (as a student in an instructional lab).  The machine used a
UNIBUS subset, for the data part.  Many of the standard PDP-16 options
(and it was all options) were originally designed for the UNIBUS.  The
basic design was an alternative to microprogramming, but with the advent
of inexpenisive ROM technology and bit-slice processor chips at about the
same time as the PDP-16 was introduced, the PDP-16 turned out to be a
poor choice.  It was, however, great fun as an instructional toy.

				Doug Jones
				[email-masked]

---

From: [email-masked] (Mattis Andersson)
Date: 22 Mar 94 08:30:01

Well, as my father owns a PDP-9, and I have been doing some maintenance on it
I should know exactly how it works. Unfortunately I have forgot some details.

The PDP-9 microprogram is real microprogram in any modern sense like in 
PDP-11 (except 11/20) or any other microprogrammed processor.

It is used to decode minor-states of DEFER, FETCH, EXECUTE etc states.
The PDP-9 fetches a new microinstruction every 212 ns or so. It is using a very
complicated delay-line system to get this timing...

The microprogram itself consists of 36 by 64 (if I remember right) E-cores.
One selects one or zero in each cell by wiring a wire through one of the 
E-cores holes. One can say that it consists of transformers, depending of
the way you enter the E-core you get a negative or poistive pulse from it.

Anyway I could check up this more when I am able to take a look at the machine
again.

I am sorry for the lousy explanation, though it's hard to explain it Swedish 
too..

Also, I think that Computer Engineering mentions something about the PDP-9
microprogram.

/Mattis Andersson

[email-masked]