Digital Equipment Corporation PDP–7

Options List

From a November 1964 Digital Equipment Corporation brochure –

"The PDP (Programmed Data Processor) 7 is a general purpose solid state digital computer designed for high speed data handling in the scientific laboratory, computing center or real time process control system.  PDP–7 is a single address, fixed 18–bit word length, binary computer using 1's complement and 2's complement arithmetic to facilitate multi-precision arithmetic.  A random access magnetic core memory with a complete cycle time of 1.75 microseconds[1] is used to achieve a computation rate of 285,000 additions per second."

Apparently a basic PDP–7 system could consist solely of a type KA77A processor, 149 core memory stack and a type KA71A I/O package and cost $45,000 in 1965.  Standard input /output equipment for a PDP–7 consisted of a Teletype KSR33 and control type 649, perforated tape reader and control type 444B, and a perforated tape punch and control type 75D.  This options list has been compiled from the DEC 1975 PDP–7 User Handbook and a 1965 price list kindly supplied by Max Burnet.  Prices are US Dollars.

Standard Input/output
75DPerforated paper tape punch and 
444BPerforated paper tape reader and 
 Second Teletype control - with KSR-33 teletype. $2,250
 Second Teletype control - with ASR-33 teletype. $2,550
172BAutomatic priority$7,000
173Data interrupt*$4,000
175Information collector*$1,000
177Extended arithmetic$6,300
KA70ABoundary register and$650
Core Memory
147Core memory module 4K, extends the first 4K$12,000
148Memory extension$8,100
149ACore memory module 4K, extends subsequent 4K$20,700
149BCore memory module 8K, extends in 8K$32,700
176Memory parity*$3,200
 Each additional 4K of memory parity. $650
197Memory increment$1,200
CR01B100Cpm card reader and*$4,100
CR02A200Cpm card reader and control (was 421A). $14,900
421BCard reader and$25,600
40Card punch controlinfo 
647Automatic line printer and$28,900
TU55Single DECtape transport. *$2,350
555DECtape dual magnetic tape*$7,400
556DECtape single magnetic tape transport.  
550DECtape control, (up to 4x 555's).info$7,800
57AAutomatic magnetic tape control, up to 8x 570s.  Requires 1x 520-22info 
520Tape control interface for DEC type 50 transport $16,200
521Tape control interface for DEC type 545 and 570 transports $18,900
522Tape control interface for DEC type 729 transport (models 2, 4, 5, 6) $21,600
570Magnetic tape$30,400
545Magnetic tape$12,000
50Magnetic tape$18,000
24Block transfer serial drum system$36,200
 Block transfer serial drum system 64K. $38,680
 Block transfer serial drum system 128K. $43,400
350Incremental plotter control*$3,000
 – with Calcomp 563 plotter $13,400
 – with Calcomp 565 plotter $8,900
34AOscilloscope display control*$2,800
 – with RM503 Oscilloscope display. *$3,600
 – with RM564 Storage oscilloscope display. *$4,540
30DPrecision CRT$13,400
33Symbol generator (characters and symbols for 30D display).info*$4,900
340Precision incremental CRT$25,800
341– with basic interface to PDP–$26,700
347– with subroutine interface to PDP–$30,058
 – modify 340 for up to four 343 Slave displays. $4,970
342Symbol generator for 340 display, first 64$7,700
 – second 64 characters. $3,900
 – each special character. $20
370High speed light$1,625
138EGeneral purpose analog to digital converter, 6-11 bits*$2,500
142High speed 10 bit Analog to digital 
139EGeneral purpose multiplexer control, 24 channel I/P for$2,000
AA03BMultiplexer expansion to 64 channels. *$300
A100Multiplexer solid-state switch module. *$165
A101Multiplexer solid-state switch module. *$178
A102Multiplexer solid-state switch module. *$86
A103Multiplexer solid-state switch module (recommended). *$153
ADA110 bit Analog digital analog converter 
AA01A12–bit Digital to Analog converter, one converter. *$1,600
 – with two D/A converters. *$2,200
 – with three D/A converters. *$2,800
174Block data 
630Data communication system, up to 8$4,500
 – with up to 64 Teletypes.  
 – add per Teletype, 2 way $535, send $275, receive $260.  
14018–bit output relay*$1,950
195Inter processor buffer (bi–directional communication to another processor).info*$3,100
KB03Device selector expansioninfo*$1,000
KB03– per IOT implemented $100
637Bit synchronous data communication$800
KP70Power failure$800
77Paper tape reader.  
KA71AI/O device package.  
KA77AProcessor unit.  
KSR-33Model 33 teletype, keyboard$900
ASR-33Model 33 teletype, asynchronous send-receive. $1,200
KSR-35Model 35 teletype, keyboard send-receive. $2,500
ASR-35Model 35 teletype, asynchronous send-receive. $4,000
CAB-1Cabinet, no end$500
 Cabinet, with end panels. $700
CAB-6Cabinet, no end panels. $600
 Cabinet, with end panels. $800

Other (custom?) PDP–7 options
OptionDescriptionWhere used
160AXNuclear Data 160 ADCSystem #113
76 05045IBM360/50 data linkSystem #113 (see below)
76 05113Eliminate auto index registers*System #113 (see below)
76 05114Change checksums*System #113 (see below)

Options * - Professor Harlan Lefevre who ran machine #113 relates that it had several options fitted by DEC including those above.  The last two were switch options to change between PDP–7 and PDP–9 checksums and eliminate the auto index registers in upper 8k core (these two option numbers may be in the wrong order).  See the page for system PDP-7/A S#113.

If you know of any information about any of the PDP–7 systems worldwide, options, location of existing systems, spare parts, ancillary bits, software, tapes or manuals, then please contact us.

All of the option descriptions have been reproduced from DEC user and maintenance manuals and are ©1972-1977 Digital Equipment Corporation

Option 75D - Perforated Tape Punch and Control.
(Standard equipment with the PDP–7) This equipment consists of a control unit and a teletype BRPE punch that perforates eight channel, fan–fold paper tape at 63.3 lines per second.   [back]

Option 444B - Perforated Tape Reader and Control.
(Standard equipment with the PDP–7) This equipment senses eight channel, fan–fold perforated Mylar or paper tape photo–electrically at 300 characters per second.  The reader is a Digitronics 2500 and the control is a DEC data register, flag, and associated logic circuits.[back]

Option 649 - Teleprinter and Control.
A Teletype Model 33 Keyboard Send Receive (KSR) set and an appropriate DEC control constitute this equipment.  The Teletype unit is a standard machine operating from serial 11–unit– code characters at rate of 10 character per second at a distance of less than 50 feet.  The Teletype provides a means of supplying data to the computer by means of a keyboard and supplies data as an output from the computer in the form of typed copy.  The Teletype control serves as a serial–to–parallel converter for Teletype inputs to the computer and serves as a parallel–to–serial converter for computer output signals to the Teletype unit.   [back]

Option 177 - Extended Arithmetic Element.
The Extended Arithmetic Element (EAE) is a standard option for the PDP–7 which facilitates high speed multiplication, division, shifting, normalizing, and register manipulation.  Installation of the EAE adds an 18–bit multiplier quotient register (MQ) to the computer as well as a 6–bit step counter register (SC).  The content of the MQ is continuously displayed on the operator console.  The type 177 option and the basic computer cycle operate asynchronously, permitting computations to be performed in the minimum possible time.  Further, the 23 EAE instructions are micro–coded so that several operations can be performed by one instruction to simplify arithmetic programming.  Average multiplication time is 6.1uS, average division time is 9uS.   [back]

Option 172B - Automatic Priority Interrupt.
The Automatic Priority Interrupt option increases the capacity of the PDP–7 to handle transfers of information to and from input/output devices by identifying and interrupt device directly, without the need for flag searching.  Multilevel program interrupts are permissible where a device of a higher priority supersedes an interrupt already in process.  These functions increase the speed of the input/output system and simplify the programming.  More and faster devices can therefore be serviced efficiently.

The type 172 option contains 16 automatic interrupt channels arranged in a priority sequence so that channel 0 has the highest priority and channel 178 has the lowest priority.  the priority chain guarantees that if two or more I/O devices request an interrupt concurrently, the system grants the interrupt to the device with the highest priority.  The other interrupts will be serviced afterwards in priority order.  Includes individual channel enable/disable registers.   [back]

Option 173 - Data Interrupt Multiplexer.
The single PDP–7 data break interrupt channel is expanded to handle information transfers with up to four high speed I/O devices by addition of the type 173 option.  This option provides multiplex control for simultaneous operation of three high speed devices such as magnetic tape or drum devices.  Maximum combined transfer rate is 570,000 18–bit words per second.   [back]

Option 175 - Information Collector expansion.
Expands the information collector (?) by an additional seven channels.   [back]

Option 197 - Memory Increment.
Option 197 allow an external condition or signal from an I/O device to increment the content of any core memory location.  The peripheral device initiates a break cycle do that the content of a core memory address specified by the device is read into the memory buffer register, incremented by one, and written back to the same address in one computer cycle.  A program interrupt is generated if the addition results in an overflow.   [back]

Option KA70A - Boundary Register and Control.
This option establishes a core memory boundary that can be assigned to specific users when the system is used for real time computing with simultaneous multi-user program execution.  A single register and control which may be set, cleared, and changed under program control.  It protects the core memory region between location 0 and the assigned boundary.   [back]

Option 147 - 4Kb Core memory module.
Extends the capacity of the standard 4096 word memory to 8192 words.  This option "fill in" the second 4096 word up to 8192Kb.  149B options are then used to further expand the system memory in 8192Kb blocks if required.   [back]

Option 148 - Memory extension control.
Memory expansion beyond a total capacity of 8K words requires addition of a type 148 option to expand the program counter, memory address register, and mode control.  Any memory size from 4096 to 32,768 words can be obtained by addition of type 147 and 149B modules.   [back]

Option 149A - 4Kb Core memory module.
Option 149A extends the capacity of the PDP–7 core memory by one field of 4096 words.  The 149A option can be added only to memories of 8K or 16K capacities.  Requires a 147 4Kb Core memory module.   [back]

Option 149B - 8Kb Core memory module.
Option 149B extends the capacity of the PDP–7 core memory by one field of 8192 words.  The 149B option can be added only to memories of 12K or 24K capacities.  Requires a 147 4Kb Core memory module.   [back]

Option 176 - Memory Parity.
This option assures the reliability of all core memory data storage and retrieval operations by generating, storing, and checking parity on every transfer.  Option adds a 19th core plane to the memory stack for the parity bit.  An odd parity bit is generated and written in the same memory location as the word being written.  Upon reading, a word drawn from core memory is checked for parity and if odd parity is detected a program interrupt is initiated or the program is halted.   [back]

Option CR01B - Card Reader and Control.
Standard 12 row, 80–column punched cards are read by this device in either alphanumeric or binary mode.  Reading is accomplished by mechanical sensors at a maximum rate of 100 cards per minute from a 430 card capacity bin.   [back]

Option 421A/B - Card Reader and Control.
Standard punched cards are read optically at up to 200 cards per minute on the type 421A, or 800 cards per minute on the type 421B.  Information punched on the cards is read column per column in binary or alphanumeric codes.   [back]

Option 40 - Card Punch Control.
This device controls on–line buffered operation of a standard card punch machine.  Cards are punched one row at a time at 40 millisecond intervals, providing a punching rate of 100 cards per minute, Any or all positions can be punched in any format.   [back]

Option 647 - Automatic Line Printer.
This option prints a selection of 64 characters on a line of 120 characters, at a rate of 300, 600, or 1000 lines per minute.  Printing is performed by solenoid actuated print hammers.  Loading, printing and format are under program control.  Format is program selected from a punched format tape in the printer.  Includes single line character buffer.  The printer is also available with up to 160 columns per line on special request.   [back]

Option 555/550 - DECtape dual magnetic tape transport (555) and control (550).
The DECtape system provides a unique fixed address magnetic tape facility for high speed loading, readout, and program updating.  Each DECtape transport contains two independent tape drives.  Up to four transports (eight drives) can be used with one control.
Read, write and search speed is 80 inches per second, Density is 375 bits per inch.  The two logically independent transports have a storage capacity of 3 million bits each.  Phase recording, rather than amplitude recording, redundant, non adjacent data track, and a pre–recorded timing and mark track are features of this system.  The control searches in either direction for specified block numbers, then reads or writes data.  Units as small as a single word may be addressed.   [back]

Option 57A - Automatic Magnetic Tape Control.
Up to eight IBM or IBM compatible tape transports can be operated automatically by the type 57A to transfer information through the PDP–7 data break interrupt facility.  Magnetic tape are controlled to read or write at densities of 200, 556, or 800 characters per inch at speeds of 75 or 112.5 inches per second.   [back]

Option 570 - Magnetic Tape Transport.
The type 570 is a highly sophisticated tape transport that reads and writes at 75 or 112.5 inches per second at program selected densities of 200, 556, or 800 characters per inch.  Tape motion is controlled by pneumatic capstans and brakes, eliminating conventional pinch rollers, clamps and mechanical arms.  Tape width is one–half inch, with six data track and one parity track.  Format is IBM compatible.  Dual read heads permit read checking while writing.  The type 570 contains a multiplex interface which permits time shared use of the transport by two type 57A tape controls on the same or different computers at transfer rates from 15 to 90kc.   [back]

Option 545 - Magnetic Tape Transport.
The type 545 magnetic tape unit operates at a speed of 45 inches per second and has three selectable densities, 200, 556, 800 bits per inch.  The 545 is controlled by the type 57A option with a type 521 interface.  Standard 7 channel, IBM compatible tape format is used.  The transport mechanism uses a pinch roller drive with vacuum column tension.   [back]

Option 50 - Magnetic Tape Transport.
The type 50 Magnetic Tape Transport can be used with the type 57A Automatic Mag Tape Control to read or write IBM compatible magnetic tapes at transfer rates of 15,000 or 41,7000 characters per second.  Tape speed is 75 inches per second at densities of 200 or 556 characters per inch.   [back]

Option 24 - Block Transfer Serial Drum System.
Drum transfers operate through the computer data interrupt facility permitting interlaced program and drum transfer operation.  Storage capacities of 32,768 words, 65,536 words, or 131,072 words are available.   [back]

Option 350 - Incremental Plotter Control.
One California Computer Products Digital Incremental Recorder can be operated from a DEC Incremental Plotter Control type 350 to provide high speed plotting of points, continuous curves, points connected by curves, curve identification symbols, letters, and numerals under program control.  The recorder can be selected from four models, that differ in speed (12,000 or 18,000 steps per minute), step size (0.1 or 0.005 inches per step), and paper width (12 or 51in).   [back]

Option 34 - Oscilloscope Display.
Computer data can be plotted point–by–point on a 5 inch oscilloscope, such as the Tektronix Model RM503, by the option.  The horizontal axis of each point is determined by 10 binary bits, and the vertical axis is determined by another 10 bits.  This option can be obtained with or without the oscilloscope.   [back]

Option 30D - Precision CRT display.
The type 30 is a random-position point-plotting display with a self contained, 16–inch CRT using magnetic deflection and focusing.  Data is plotted point by point in a raster 9–3/8 inches square having 1024 on a side according to separately variable 10–bit X and Y coordinates.  The display includes program intensity control.  Plotting rate is 35 microseconds per point.   [back]

Option 33 - Symbol Generator.
The type 33 Symbol Generator is an option used with the type 30 display that simplifies the programming require to present character and symbols on the face of the display tube.  Plots symbols on a 35 dot (5x7) matrix in one of four sizes, average plotting time is 140uS.   [back]

Option 340 - Precision Incremental CRT Display.
Plots points, lines, vectors, and characters on a raster identical to the model 30.  Plotting rate is 1.5 microseconds per point in vector, increment and character modes.  Random point plotting is 35 microseconds.  Requires interface type 341 or 347.   [back]

Option 342 - Symbol Generator.
The type 342 Symbol Generator serves a similar purpose as the type 33 but is used for plotting on the type 340 display.  Plots symbols on a 35 dot (5x7) matrix in one of four sizes, average plotting time is 35uS.  Two 64 character sets are available for the type 342.   [back]

Option 343 - Slave Display.
Includes 25 feet of remote cable.  Additional cable at $1.50 per foot.   [back]

Option 370 - High speed Photomultiplier Light Pen.
A fiber optic light pipe and photomultiplier in the light pen allow high speed detection of information displayed on the type 34A, 30D, or 340 displays.  Detection of information by the type 370 can be sampled by the computer to alter the program.   [back]

Option 138 - Multi-purpose analog to digital converter
Option 138 is a high speed successive approximation converter with an analog input signal range of 0–10V.  The analog voltage is converted to a binary number, selectable from 6–12 bits, and conversion times from 9uS–35uS.  Conversion time varies depending on the number of bits and the accuracy required.  Combinations of switching point accuracy and number of bits can be selected on a front panel switch.   [back]

Option 142 - High speed 10 bit Analog to digital converter.
Transforms an analog voltage to a single, 10–bit binary number in 6uS.  Conversion accuracy is +/-0.14% +/-1/2 least significant bit.   [back]

Option 139E - General purpose multiplexer control, 24 channel I/P for option 138 or 142.
With the AA03 expansion option up to 64 analog input channels can be selected for application to the input of a 142 or 138E option.  Channels can be program selected in sequence or by individual address.  The number of channels that can be selected is determined by the number of optional multiplexer switches (A100) used in the 139E, each A10x can select two channels.  Prices of input switches are not included.   [back]

Option ADA1 - Analog-Digital-Analog Converter System.
This option performs fast, real-time conversion between digital and analog computers.  Maximum sample rate for D/A conversion is 200kc; for A/D and interlaced conversions, 100kc.  Digital word length is 10 bits.  Actual conversion times are 5 microseconds for A/D and 2 microseconds for D/A.  Semiautomatic features enable the converter system to perform many of the functions that a computer normally performs for other converter interfaces.   [back]

Option 174 - Block Data Control.
The Block Data Control option controls and buffers the transfer of data blocks between the PDP–7 and up to three external devices.  Block transfers are made from consecutive memory locations one device at a time.  The data control counts the number of data words transferred, buffers either incoming or outgoing information until the transfer is complete and signals the completion of a transfer.  Maximum data transfer rate is 1.75 microseconds per 18–bit word, or 570,000 18–bit words per second.   [back]

Option 630 - Data Communications Systems.
This system is a real-time interface between Teletype stations and the PDP–7 and is ideal for multi-user time-sharing message switching systems, and data collecting-processing systems.  Available in two models, the smaller system is expandable to 8 stations, whilst the larger system is expandable to 64 stations.  A variety of type 630 are available for half–duplex and full–duplex operation.   [back]

Option 140 - 18–bit output relay buffer.
A data buffer loaded from the computer accumulator activates 18 relays, each having Mercury-wetted single-pole double throw contacts.  These contacts can be used for direct digital control or signal generation for external equipment.   [back]

Option 195 - Inter Processor Buffer.
This device serves as an interface between a PDP–7 and another computer to permit bi–directional data communication with another asynchronous processor.   [back]

Option LT33 - Teletype Model 33 KSR.
(Standard equipment with the PDP–7) The Teletype Model 33 KSR (keyboard-send-receive) can be used to type in or print out information at the rate of 10 characters per second.  Signals transferred between the 33 KSR and the keyboard printer control logic are standard serial, 11 unit code Teletype signals.  The signals consist of marks and spaces which correspond to idle and bias current in the Teletype and zeros and ones in the control and computer.  The start mark and subsequent eight character bits are one unit of time duration and are followed by a two unit stop mark.  Each of the (64 type) characters and 32 control characters are represented by an 8–bit standard ASCII code.   [back]

Option CAB - Cabinets.
Prices of options marked with an asterisk (*) do not include a cabinet.  If there is space for these options in cabinets required for other portions of the system, no additional cabinets need be purchased.  If the total price of all options marked with an asterisk (*) is at least $10,000, a cabinet will be supplied at no charge, otherwise a cabinet must be purchased.   [back]

Option 15780 - Multiplexer switches.
Module containing four independent transistorised floating switches.   [back]

Option 637 - Bit synchronous data communication system.
Also known as a 637 Data Communication channel.   [back]

Option KB03 - Device Selector Expansion.
Expands the basic device selector by up to a maximum of ten additional selectors.   [back]

Option KP7B0 - Power Failure Detection.
Senses the power lines and provides a signal if a power failure is about to occur in time to allow program storage of all active registers.   [back]

Option 341 - 340 Display Basic Interface.
Precision incremental CRT display with basic interface to PDP–7.  Provides sequential access to a single block of data in the computer core memory.   [back]

Option 347 - 340 Display Subroutine Interface.
Precision incremental CRT display with subroutine interface to PDP–7.  Adds logic for address manipulation between non–consecutive display tables.[back]

  1. A find in DECuscope Volume 10 1971, the newsletter of the Digital Equipment Users Society, has unearthed an article by A. R. Atherton of the Cavendish Laboratory, Cambridge, England (PDP–7/A S#126), entitled "MODERNIZING A PDP–7", where a new 16K core store was fitted to their PDP–7 and the opportunity taken to reduce the cycle time of the computer from 1750 nsec to 875 nsec, doubling its speed.[top]

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