Subject: FAQ

From: [email-masked] (Douglas W. Jones,201H MLH,3193350740,3193382879)
Date: Fri, 2 Oct 1992 17:50:13 GMT

This is a trial posting of a FAQ for this newsgroup.  I'd appreciate any
and all comments I can get.   In particular, I'd like to get the original
list price for a minimum configuration of each make and model of the -8,
the sales volume for each, and the accurate end-points for the production
run for each.

================= begin trial posting of FAQ ==================

Frequently Asked Questions about the PDP-8

	By Douglas Jones, [email-masked]

What is a PDP?

	For over a decade, all programmable digital computers sold by
	Digital Equipment Corporation were sold as Programmable Data
	Processors (PDPs) instead of computers.  I have DEC documentation
	that actually calls them "PDPs", so this is not improper usage.
	The name was chosen because the first DEC computer, the PDP-1,
	had a selling price of $120,000 when competing machines were
	selling for over $1,000,000.  Everyone knew that computers were
	big and expensive and needed a computer center and a large staff,
	and DEC was trying to sell something relatively inexpensive that
	didn't need such support facilities.  DEC chose to deal with these
	steriotypes by avoiding the term "computer" entirely in their
	sales efforts.

	DEC built a number of different computers under the PDP label,
	of which the PDP-8 family machines were the smallest and least
	expensive.  The PDP-10, for example, was a large machine worthy
	of a computer center and large support staff.  The PDP-14 wasn't
	even a computer -- it was a ROM based industrial controller.
	The PDP-11, a 16 bit minicomputer/microprocessor family, is the
	only DEC product still being sold under the PDP name.

What is a PDP-8?

	The PDP-8 family of minicomputers were built by Digital Equipment
	corporation between 1965 and 1990.  These machines were
	characterized by a 12 bit word, with no hardware byte structure,
	a 4K minimum memory configuration, and an extremely simple
	instruction set.  By 1970, the PDP-8 was the best selling computer
	in the world, and many models of the PDP-8 set new records as the
	least expensive computer on the market.  The PDP-8 has been
	described as the model-T of the computer industry.

	Gordon Bell (who later was chief architect of the PDP-11 and
	who, as Vice President, oversaw the development of the VAX) says
	that the instruction set of the PDP-8 was not really original
	with him.  He credits Seymour Cray (of CDC and later Cray) with
	the original idea.  Cray's CDC 160 family, sold starting around
	1959, was a very similar 12 bit minicomputer, and the peripheral
	processors of Cray's first supercomputer, the CDC 6600, also look
	very familiar to PDP-8 programmers.

	The following basic models of the PDP-8 were sold by DEC:

	MODEL	DATES	SALES   COST	TECHNOLOGY	COMPATABILITY

	PDP-5	63-65			Transistor	Limited
	PDP-8	65-68 	>1000	<$100K	Transistor	Full
	LINC-8	66?	>500?	<$100K	Transistor	Full (1)
	PDP-8/S	67?	>1000?	<$10K	Transistor 	Limited and slow!
	PDP-8/I	68?	>2000?	<$100K	TTL		Full
	PDP-8/L	68?	>2000?	<$100K	TTL		Full (2)
	PDP-12	69?	>1000?	<$100K	TTL		Full (3)
	PDP-8/E	70-78	>10K	<$10K	TTL MSI	Omnibus	Full (4)
	PDP-8/F	73-78?	>10K?	<$10K	TTL MSI Omnibus Full (uses 8/E CPU)
	PDP-8/M	73-78?	>10K?	<$10K	TTL MSI Omnibus Full (an OEM 8/F)
	PDP-8/A	75-84?	>10K?	<$10K	TTL LSI Omnibus Full (new CPU) (5)
	VT78	78-80	>	?	Microprocessor  Full (Intersil IM6100)
	Dm I (6)80-84			Microprocessor	Full (Intersil IM6120)
	Dm II				Microprocessor	Full
	Dm III	84-90			Microprocessor	Limited expansion
	Dm III+	8?-90			Microprocessor	Limited expansion
			(7)

	Notes	(1) The LINC-8 combined a modified PDP-8 with extenstions
			supporting compatibility with the Laboratory
			Instrumentation Control Computer developed at
			Lincoln Labs in the early 1960s.
		(2) The PDP-8/L was intended as a scaled down version of
			the PDP-8/I, and most of them had only 4K memory,
			but eventually, a full range of upgrade options
			were sold.
		(3) The PDP-12 was originally designated the LINC-8/I; it
			was a follow-on to the LINC-8.  It had the most
			impressive control panel of any 8-family machine.
		(4) The PDP-8/E is considered by many to be the definitive
			model of the PDP-8.
		(5) After 1978, Reuters bought almost all of the remaining
			PDP-8/A production run (5-6 years at 1000/month).
		(6) Dm stands for DECmate.
		(7) The total sales figure for the PDP-8 family is
			estimated at over 300,000 machines.  Over 8500
			of these were sold prior to 1970.

	The above list does not include many PDP-8 variants sold by DEC
	to meet the needs of various special users.  For example, the
	Industrial-8 was really just a PDP-8/E with a different nameplate
	and color scheme.  In addition, DEC made many peripheral
	controllers for the PDP-11 and PDP-15 that used IM6100
	microprocessors.

	The following PDP-8 compatable or semi-compatable machines were
	made and sold by others; very little is known about many of these:

	MODEL		DATE	MAKER, NOTES

	MP-12		6?	Fabritek
	DCC-112		6?	Digital Computer Controls
	DCC-112H	6?	Digital Computer Controls
	TPA		68?	Hungarian, possibly a DEC PDP-8/L in drag
	6100 Sampler	7?	Intersil, their promotional kit
	Intercept	7?	Intersil
	Intercept Jr	7?	Intersil
	SBC-8		84-88	CESI, Based on IM6120, SCSI bus

Where can I get a PDP-8 today?

	The CESI machine may still be on the market, for a high price, but
	generally, you can't buy a new PDP-8 anymore.  There are quite a
	few PDP-8 machines to be found in odd places on the used equipment
	market.  They were widely incorporated into products such as
	computer controlled machine tools, X-ray diffraction machines, and
	other industrial and lab equipment.  Many of them were sold under
	the EduSystem marketing program to public schools and universities,
	and others were used to control laboratory instrumentation.
	Reuters bought the tail end of the production run.

	If you can't get real hardware, you can get emulators.  Over the
	years, many PDP-8 emulators have been written; the best of these
	are indistinguishable from the real machine from a software
	prespective, and on a modern high-speed RISC platform, these
	frequently outperform the hardware they are emulating.

Where can I get PDP-8 documentation?

	The 1973 Introduction to Programming was probably DEC's definitive
	manual for this family, but it is out of print, and DEC was in the
	habit of printing much of their documentation on newsprint with
	paperback bindings, which is to say, surviving copies tend to be
	yellow and brittle.

	DEC distributed huge numbers of catalogs and programming handbooks
	in this inexpensive paperback format, and these circulate widely
	on the second-hand market.  Whe research laboratories and
	electronics shops are being cleaned out, it is still common to
	find a few dusty, yellowed copies of these books being thrown in
	the trash.

	Maintenance manuals are harder to find, but more valuable.
	Generally, you'll need to find someone who's willing to photocopy
	one of the few surviving copies.  Fortunately, DEC has been
	friendly to collectors, granting fairly broad letters of permission
	to reprint obsolete documentation, and the network makes if fairly
	easy to find someone who has the documentation you need and can
	get copies.

What operating systems were written for the PDP-8?

	A punched paper-tape library of stand-alone programs was commonly
	used with the smallest (diskless and tapeless) configurations from
	the beginning up through the late 1970's.  Many paper tapes from
	this library survive to the present at various sites!

	The DECtape Library System was an early DECtape oriented save and
	restore system that allowed a reel of tape to hold a directory of
	named files that could be loaded and run.  Eventually, this
	supported a tape-to-tape text editor and it could be used for
	on-line program development.

	The 4K Disk Monitor System provided similar facilities using disks
	or DECtape.  This supported on-line program development and it
	with any device that supported 129 word block sizes.

	MS/8 or the R-L Monitor System, developed starting in 1966 and
	submitted to DECUS in 1970.

	P?S/8, developed starting in 1971 from an MS/8 foundation.  Runs
	on minimal PDP-8 configurations, supports device semi-independant
	I/O and a file system on a random-access device, including DECtape.

	OS/8, developed in parallel with P?S/8, became the main PDP-8
	programming environment sold by DEC.  The minimum configuration
	required was 8K words and a random-access device to hold the
	system.

	TSS/8 was developed in 1968 as a timesharing system.  It required
	a minimum of 12K words of memory and a swapping device.  It was
	fairly widely sold to support educational timesharing.

	Other timesharing systems developed for the PDP-8 include MULTI-8,
	ETOS, and OMNI-8; these were similar to TSS/8, and by the mid
	1970's, many of these were true virtual machine operating systems
	in the same spirit as IBM's VM-370.

	WPS was DEC's word processing system that was widely used on the
	1980's vintage machines with a special WPS keyboard replacing the
	standard keyboard.

What programming languages were supported on the PDP-8

	The PAL family of assembly languages were as close to a standard
	assembly language as can be found for the PDP-8.  These produced
	absolute object code and versions of PAL would run on minimally
	configured machines.

	MACRO-8 was DEC's first macro assembly language for the PDP-8, but
	it was never used outside the paper-tape environment.  MACREL and
	SABR were assembly languages that produced relocatable output;
	these were developed to support different FORTRAN compilers.  SABR
	was used as a final pass for DEC's FORTRAN compilers.

	A subset of FORTRAN was supported on both the PDP-5 and the
	original PDP-8.  Surviving documentation describes a DEC compiler
	from 1964 and a compiler written by Information Control Systems
	from 1968.

	RTPS FORTRAN contained real-time extensions and was a full
	FORTRAN IV (ANSI FORTRAN 66) implementation.  Some later DEC
	documentation refers to 4K FORTRAN and 8K FORTRAN; the former
	is the old subset compiler, the latter is a reference to the
	code descended from RTPS FORTRAN.

	FOCAL, an interpretive language comparable to BASIC was available
	on all models of the family, including the PDP-5 and PDP-8/S.

	BASIC was also available, and was widely used on PDP-8 systems
	sold under the EduSystem marketing program.  A version was
	available that ran in 4K, and there was an 8K time-sharing
	version.

	Algol was available from a fairly early date.

	At least two Pascal compilers were developed for the PDP-8.

	At least two LISP interpreters were written for the PDP-8; one
	runs in 4K, the other can use up to 16K.

	TECO, the text editor, is available, and is also a general purpose
	language, and someone is working on a PDP-8 C.

Where can I get PDP-8 software?

	DECUS, the DEC User Society, is still alive and well, and their
	submission form still lists PAL-8 and FOCAL as languages in which
	they accept submissions!

	There is a young but growing FTPable archive of PDP-8 software at
	ftp.telebit.com in directory /pub/pdp8.

Where can I get additional information?

	The file WHAT-IS-A-PDP8, by Charles Lasner contains considerable
	additional information; this file is included in the FTPable
	archive cited above.  This file gives details of every model
	of the PDP-8, including the small quirks and incompatabilities
	that (to be generous) allow software to determine which model it
	is running on.  These quirks also make it all too easy for
	careless programmers to write almost portable software with very
	obscure bugs.

	The mailing list [email-masked] reaches a number of PDP-8
	owners and users, not all of whom have USENET feeds.  The USENET
	newsgroup alt.sys.pdp8 is fairly new, but someday, the newsgroup
	and mailing list will be gatewayed to each other.

	Many "archival" books have included fairly complete descriptions
	of the PDP-8; among them, "Computer Architecture, Readings and
	Examples" by Gordon Bell and Allen Newell is among the most
	complete (and difficult to read).  Considering Bell's role in the
	design of the PDP-8 and the history of DEC, the description in
	this book should be accurate!

---

From: [email-masked] (Bob Pasker)
Date: Fri, 2 Oct 1992 23:27:59 GMT

>	steriotypes by avoiding the term "computer" entirely in their

one nit to pick: olson et al chose not to call their machines
"computers" because the investors would have then refused to buy in.
ostensibly, they felt that the cmputer field would be less lucrative
than makeing modules, like the "flip-chip."  could be urban legend, 
could be truth, but its at least plausible.  someone call ken and
ask him.

-- 
--- bob pasker
---- [email-masked]

---

From: [email-masked] (Charles Lasner)
Date: Mon, 5 Oct 1992 07:54:14 GMT

>could be truth, but its at least plausible.  someone call ken and

The notion about PDP's versus computers sounds plausible, but does anyone
have any info about it?

In any case, the Flip-Chip notion is a legend in itself.  For some reason,
undue emphasis is given to a detail of the implementation of some module
series, mostly R-series, but S and probably B as well *might* have this.

Flip-Chips are the small hybrid packages that are sometimes used on some of the
cards which are used in the early models of PDP-8, -10, -9, LINC-8, etc. in
these three main module series.  They are *never* a requirement for most 
modules.  If you pickup a random R-series module, it has transistors and
diodes and resistors and capacitors on it, no Flip-Chips at all.  Some of
the cards do substitute a little thick-film hybrid package for some of
the diodes, resistors and capacitors, essentially the components that make
up the so-called DCD gate commonly used in the logic.  The purpose is to
standardize the signals between cards, and is essentially a way to get
a level and/or a pulse as input to a flip-flop or gate.  Today we would just
have edge and level-triggered flip-flops where necessary.  In any case, some
of the leads of the DCD gate are component interconnect, so it can be looked
upon as a module.  DEC eventually did make Flip-Chip modules, so on certain
cards, you find these little packages in lieu of the standard set of components
which doesn't dramatically cut down on either parts count or even lead count.
In fact, many of the Flip-Chips have proven to be unreliable and have to be
replaced with the normal complement of discrete components when repairing the
module.  All of them are readily available: silver-mica capacitors, 1/4 Watt
resistors and miniature silicon diodes are all that constitutes what's in a 
Flip-Chip.

Eventually, some "evil" modules appeared.  They usually have numbers like
R107 s1a where the s1a means that someone bothered to relayout the module so
it can *only* take Flip-Chips :-(.  (As opposed to the earlier design which
could take either the loose components or the same exact parts count as the
newer ones.  The only difference from a manufacturing standpoint is the
arbitrarily different etch and a modestly smaller drilled-hole count.  Hardly
worth offseting the cost of the redesign.)

For these modules, repair is more difficult.  In an pinch, the components can
be soldered together to make a Flip-Chip "equivalent" and then the whole bunch
is inserted into the Flip-Chip's solder holes.  Alternatively, a working
earlier card gets "cannabalized" for Flip-Chips to fix the Flip-Chip-only card.
The earlier design is then refitted with the loose components it is designed
to take.  When done, you have a working newer s1a card, and an older card
returned to older-still standards.

So, descriptions of clean rooms, etc. aside, Flip-Chips per se play a
secondary role in the production of modules sometimes described as "Flip-Chip
modules" which may be 100% devoid of Flip-Chips.  Moreover, some modules such
as R001 and R002 which only contain diodes, never have Flip-Chips.  Can anyone
post the suffix variation for some of these cards that indicate that the
card also lacks the diodes?  (Yes, I saw one of these once.  It wasn't s1a, but
some other suffix meaning all components deleted!)  To my knowledge, there
isn't a single R, S, or B-series module which *only* came in Flip-Chip-bearing
variety.  Moreover, Flip-Chips only came in a few standard configurations, 
since they only replaced certain component sets, thus cards tended to have
some discrete components anyway.  And they *never* replace the discrete
transistors used on the module.

cjl (in possession if literally thousands of R-series modules)

---

From: [email-masked] (Douglas W. Jones,201H MLH,3193350740,3193382879)
Date: Mon, 5 Oct 1992 13:47:02 GMT

>From article <[email-masked]>,
> series, mostly R-series, but S and probably B as well *might* have this.

There's another side to this legend, though.  Originally, in the 1965 era,
the word flip-chip was a reference to the hybrid integrated circuits DEC
was trying to use.  By the end of the decade, though, DEC was assertively
referring to the logic modules themselves as flip chips.  Thus, every M
series logic module I've got seems to say FLIP CHIP across the top of the
module right under the handle (except the M211, which says DEC FLIP CHIP).
It seems clear that by 1970, DEC wanted people to call the modules
themselves flip chips.

On another topic, IBM, with the introduction of the IBM System 360 in 1965,
declared the birth of the third generation of computers.  (The number 360
was a marketing ploy in itself, standing for "a third generation machine
for the 1960's"; that's why they had to renumber to 370 when the new decade
came.)

IBM said that third generation machines were characterized by integrated
circuits, but the System 360 only had hybrid integrated circuits, not
monolithic circuits.  By this standard, the Classic PDP-8 could be called
a third generation machine!
				Doug Jones
				[email-masked]

---

From: [email-masked] (Charles Lasner)
Date: Mon, 5 Oct 1992 18:22:37 GMT

>It seems clear that by 1970, DEC wanted people to call the modules

Absolutely.  DEC exaggerated the importance of the original Flip-Chips to the
point that they had to support the name for virtually the entire product line
of modules, whether Flip-Chips were part of the construction or not.

But if you look at the early literature, such as the somewhat hyped pictures
in the early Logic Handbooks, etc., it's clear that they are intending to
focus in on DEC's "high-tech" production capabilities of Flip-Chips, and to
take the focus away from the ordinary techniques that DEC, as a module maker,
used to produce modules no better or worse than a dozen other module houses.
This is likely a carry-over from an earlier era when DEC wasn't a computer
maker but rather a module-only house for other companies.  Can anyone cite a
specific machine from another company that was actually made out of DEC modules
but wasn't "heralded" as such (Circa 1957-1961 in all probability).

BTW, I have a relatively rare publication about Flip-Chips.  Before them, DEC
made only Systems Modules, which are much larger and always using discrete
components.  They are characterized by aluminum frame strips, larger connectors
and all-digit module numbers.  The handbook that describes them is an 8.5 x 11"
book of overall higher quality than most later DEC paper-backs such as the
Logic Handbooks.  There was a singular "transition" publication which is
essentially the precursor to the entire family of Logic Handbooks that 
discusses Flip-Chip modules; it's a 1964 Flip-Chip Handbook and is of the
same quality.  Because the paper quality is so much better, it has not yellowed
and the thick paper stock binding hasn't broken.  The one year or more newer
Logic Handbooks have all since deteriorated severely :-(.

cjl

---

From: [email-masked] (Bob Pasker)
Date: Tue, 6 Oct 1992 03:23:16 GMT

-- 
--- bob pasker
---- [email-masked]

---

From: [email-masked] (Douglas W. Jones,201H MLH,3193350740,3193382879)
Date: Tue, 6 Oct 1992 14:08:16 GMT

> But if you look at the early literature, such as the somewhat hyped
> pictures in the early Logic Handbooks, etc., it's clear that they are
> intending to focus in on DEC's "high-tech" production capabilities of
> Flip-Chips, and to take the focus away from the ordinary techniques
> that DEC, as a module maker, used to produce modules no better or worse
> than a dozen other module houses.

Yes.  The loose-leaf notebook "Digitial Flip-Chip Modules, First Revision,
July 1965, C-105 7/65" is full of such hype.  They have nice photos of
such things as hand-assembly of hybrid circuit modules -- from a modern
semiconductor manufacturing perspective, it's really quite quaint!

> BTW, I have a relatively rare publication about Flip-Chips.

I think I just cited the second edition of the same publication!  It's a
pity that DEC didn't stick to this format, because it's refreshing to see
old DEC documentation that's not yet yellowed and crumbling!  Is there a
need for a tutorial on how to rescue old manuals when they reach this state?
I've done reprints of one DEC handbook on archival paper, and I'm willing
to share the art!
					Doug Jones
					[email-masked]