From: jones@pyrite.cs.uiowa.edu (Douglas W. Jones,201H MLH,3193350740,3193382879)
Subject: FAQ
Date: Fri, 2 Oct 1992 17:50:13 GMT
Organization: University of Iowa, Iowa City, IA, USA

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, jones@cs.uiowa.edu

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 pdp8-lovers@ai.mit.edu 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!
Newsgroups: alt.sys.pdp8