![[PDP-8 straight]](8_coveredx.jpg)
Word Length: 12 Bits
Clock cycle time: 1.5 microsecond
Primary memory: 4K 12-bit word core memory
Secondary memory: 32K maximum
Instruction set: 3-bit op code, 1 indirect bit; 8 bits of address
Original I/O: teletype (ASR-33) with paper-tape reader/punch
AC Power: 780 watts
weight: around 250 pounds
1965 Price: $18,000 (equivalent 2008: $123K based on CPI)
Produced by Digital Equipment Corporation (DEC), now part of HP
The DEC PDP-8 is generally considered to be an (or THE) important minicomputer of the 1960's, due to its relative low cost, small size and relatively large production (about 1500 for this model, 50,000 in all models).
This "straight 8" PDP-8 system is serial number 1158, probably constructed in late 1967. The core stack was dated late 1967. This is called a "straight-8" because it is the first model of the 8 series and constructed of transistorized modules. Later 8's were made from integrated circuits and later as a microprocessor. These were often sold with a model 33 Teletype, a mechanical printing terminal which used 1-inch wide punched paper tape to store and recall data and text.
The "8" and a KSR33 Teletype was donated in 1969 by DEC to the "R.E.S.I.S.T.O.R.S", a high-school computer club founded in 1967 in Hopewell, New Jersey USA. The name comes from "Radically Emphatic Students Interested in Science, Technology, and Other Research Subjects". They were mentored by Claude Kagan, an engineer at Western Electric who predicted inexpensive home computers in his "Home Reckoner" article in 1973 - years before the first microcomputer.
The RESISTORS took the computer to a number of professional computer shows and demonstrated Claude's "SAM 76" language. They attached a pair of wooden handles to make it "portable". SAM 76 allowed for efficient programming and calculation on small computers and later microcomputers; just as BASIC did on microcomputers several years later. Professional programmers and engineers were shocked to see teens write programs on a "small" computer and get serious results - in 1970!
In April 2008, Claude Kagan, and those RESISTORS he could contact, agreed to offer the PDP-8, the Teletype, and a ??? Calcomp plotter to MARCH and InfoAge. MARCH is a vintage computer club, residing at the InfoAge science center facilities at the former Camp Evans Army Base in Wall NJ. Camp Evans is itself a National Historic site for communications and computing work through the 20th century.
MARCH exhibited the 8 on the day of acquisition, at the 2008 Trenton Computer Festival. Claude Kagan spoke at the TCF on "Evolution of a Computer Language" and was honored as the 2007 "Hobbyist of the Year" for his work with the RESISTORS. The PDP-8 and Teletype will be exibited at MARCH's facility at InfoAge in Wall, NJ, USA.
system with left cover on from left
uncovered system from front
front panel
image of rightside compared to human head
...head on left is Herb Johnson; persons on right is Claude Kagan and Evan Koblentz of MARCH
right-side image showing card tabs
higher resolution right-side image
left-side image showing card tabs
higher resolution left-side image
card tops note "10 67" month/year code
A704 card, 10-volt reference supply
Calcomp ??? plotter
RESISTORS club Web site
more RESISTORS history
Wikipedia's description of SAM76
Wikipedia entry for Claude Kagan
Home Reckoner publication
Bill Degnan's MARCH/TCF photos
MARCH computer club
InfoAge
Trenton Computer Festival
Wikipedia and PDP-8
Frequently Asked Questions about PDP-8's (technical)
price and function list for DEC modules, from which "straight" PDP-8's were constructed.
A Web search for "PDP-8" will find many sites, and private and public museums, which describe and support this computer even today. Several 8's are still operational and some have sold for many thousands of dollars (2008).
The Calcomp drum-based pen plotter is of interest to many vintage computerists, as it was used on many systems. Stepper motors moved the paper drum in rotation, and the pen mechanism across the pair of rails. A solenoid pushed the pen "up" or "down" to make contact with the paper. Paper was fed from one roll and taken up on another roll.
The RESISTOR's donated plotter, and other MARCH member's plotters, are imaged below. Following that are links to sites with Calcomp plotter information.
photos
RESISTORS's Calcomp plotter
RESISTORS's Calcomp plotter pen photo #1
RESISTORS's Calcomp plotter pen photo #2
RESISTORS's Calcomp plotter pen photo #3
RESISTORS's Calcomp plotter pen photo #4
Calcomp plotter pen holder, from manual
Herb Johnson's Calcomp 565 plotter
Herb Johnson's Calcomp 565 plotter, rear jacks
links:
"big brother" model 563, owned by PDP-8 owner David Gesswein
David's PDP-8/I at MARCH's VCF-EAST in 2007
the IBM 1627 version, used on the IBM 1130 (link courtesy of Jeff Jonas, who has this model)
As of May 4 2008: Evan Koblentz will photograph the ID plate on the Kagan/MARCH plotter Both Jeff Jonas and David Gesswein have offered to photograph more details about the pen holder on their Calcomp plotters. Herb Johnson has offered to check out and work on the Kagan/MARCH plotter.
There is discussion about the Calcomp plotter and the Kagan PDP-8 in the MARCH Yahoo! mail list. You can find it via Yahoo! or via the MARCH Web site link at the top of this Web page.
contact the author via email links at this Web page
Copyright © 2008 Herb Johnson except photos by Bill Degnan
