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Document:	dec.pdp4.1963.102646216
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Pages:	16
Original Filename:	dec.pdp4.1963.102646216.pdf

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PROGRAMMED DATA PROCESSOR -4
F-41D

PRPORATION

MAYNARD, MASSACHUSETTS

Programmed Data Processor-4 has been
developed to meet the requirements of the
engineeringand scientific profession. Special emphasis has been placed on a powerful input-output interface in the computer.
Extensive applications in the system control and data reduction fields are well
within PDP-4's capability.
Copyright 1963 by Digital Equipment Corporation

Programmed Data Processor-4 (PDP-4) is a general purpose, high speed, solid state
computer designed to be the control element in an information processing system or a complete
scientific computer. It is a single address, parallel, binary machine with an 18-bit word length
using 1's or 2's complement arithmetic. A random access magnetic core memory with a complete cycle time of 8 microseconds is used to achieve a computation rate of 62,500 additions
per second. Other features include:
FORTRAN II COMPILER Including symbolic assembly with debugging and floating
point arithmetic packages.

RTU- TlME CONTROL Provides buffering and control for multiple input-output con.
nections, program and data interrupt facilities, and a real time clock.
MULTIPLE AUTO-INDEXING Eight Auto-Indexing Memory locations simplify programming and increase the speed of table look-up and other routines.

HIGH SPEED OPERATION Basic instructions require only 8 or 16 microseconds to be
completely executed.
LINK BIT Provides facilities which simplify and speed up multiple precision
operations.

STANDARD IN-OUT OPTIONS Magnetic Drums, Display Scopes, Magnetic Tape, Line
Printers, Punched Cards, Punched Tape, and Analog Converters.

ECONQMICAL MEMORY EXPANSION Provision is made for memory expansion up
to 32K.

EXTENDED ARITHMETIC UNIT (OPTIONAL) Adds 23 instructions to a standard
PDP-4 including Multiply, Divide, Normalize and Long-Shift.

v
REAL TIME CONTROL

P-4 SYSTEM DIAGRAM

I I

STANDARD PDP-4
The PDP-4 includes all essential elements for
optimum performance as a systems component.
The standard machine consists of:

&
PRUUSfJOR - which performs
arithmetic operations, controls the memory,
and handles information entering and leaving
the machine;

k REAL TIM€ QO.NTJlOL which provides the
computer with an additional capability to operate a large variety of input-output devices with
different information handling rates.

AN OPERATOR CONSOLE - which contains all
controls needed to observe and modify the status of the Central Processor;

A PAPER TAPE READER
which permits
information and instructions to be read from 5,
7 or 8-hole perforated paper tape into the Central Processor at the rate of 300 lines per
second.

A.4#6-WaRD MEMORY- which provides storage for information being collected or distributed and instructions for the Central Processor;

Various options which extend the usefulness of
the PDP-4 are described on Pages 7, 8 and 9.

CENTRAL PROCESSOR
OPTIONS
~RST
EXTRA -warn
GO* MEMOW MODULE-TYPE

I ~ C

8 L W N r k u v s DRUM
~~ W m -

TYPE 24

The Type 134 extends the memory capacity of
the PDP-4 from 40% to 8192 words. Additional
modules require the use of a memory extension
control (see below).

The drum system operates on a serial transfer
basis in 256-word blocks. It is available in three
capacities: 16, 32, 65 thousand words.

COR€ WEMOW NIUDUW-WW 13s

WPB 18

The Type 135 extends the memory capacity of
the PDP-4 by 8192 words.

The Extended Arithmetic Element (EAE) adds
23 micro coded instructions to PDP-4 which facilitate high speed multiplication, division, and
shifting. The EAE contains an 18-bit register,
the Multiplier Quotient (MQ); a 6-bit register,
the Step Counter (SC); and a 3-bit Instruction
Register.

GORE MERlORY EXTENSION
C-L-TYPE
16
The Type 16 extends the memory control capability of the PDP-4 from 8192 to 32,768 words.

-DEB

ARtTflMETiC EUMEPT-

REAL TlME CONTROL
The Real Time Control of the PDP-4 provides
the following functions:

DEVICE SELECTION - consists of decoding
elements to select and control external devices
by various combinations of input-output transfer instructions. Pulses may be used to: (a)
control external devices; (b) read out information from PDP-4 through the lnformation Distributor; (c) read in information to PDP-4 through
the lnformation Collector, and (d) test the status
of external devices.

INFORMATION COLLECTION - information is
received from input devices (selected by the
Device Selector) and is transferred to the Central Processor. lnformation is read in parallel
(up to 18 bits) from multiple inputs.

INFORMATiON DISTRIBUTION
permits distribution of information from the Central Processor to all output devices. Only the output
device selected (or addressed) by the Device
Selector samples and reads the information
contained in the lnformation Distributor.

IN-OUT SKIP FACILITY - provides program
skip instructions conditioned by the state of
input-output device logic lines. The instruction
following a skip instruction will not be executed
if the line is active.

PROGRAM INTERRUPT - permits conditions
from input-output devices to interrupt the program and initiate a subroutine which may return
to the original program when the cause for interruption has been processed. The machine
state is preserved during a Program Interrupt.
This type of interrupt is suited for information
or event rates in the range of 1 to 2,000 cycles
per second.

DATA INTERRUPT
allows a device to interrupt the program and deposit or extract data
from the Core Memory at an address specified
by the device. The Data Interrupt is suited for
high speed information transfers. Up t o 125,000
18-bit words may be transferred per second.

REAL TIME CLOCK - produces a signal which
increments a Core Memory register at a rate of
60 cycles per second. When the register overflows, a Program Interrupt occurs.

INPUT-OUTPUT OPTIONs
Cathode Ray Tube Displays
either graphical or tabular data. Separately
variable 10-bit X and Y coordinates and programmable intensity control.

LIGHT PEN-TYPE 32
A photoelectric device with which the operator
can sense displayed data and input modifying
signals to the computer. The computer can then
change its operation according to previously
programmed instructions.

DTBNAL $WtWL t3EWRWWR-

- m e sm

Automaticafty translates digital computer words
into format information for display. Plots symbols on a 35-dot matrix in one of four sizes on
the Type 30 CRT Display. Average plotting rate:
140 microseconds per symbol.

PRBClSlON CRT DT@FtAY-TYPE WD.
Displays data on a 16-inch cathode ray tube.
Information is plotted point by point to form

osmuoscow ~ P W - w e raa
Plots data point by point on a Textronix oscilloscope. Ten bits per axis. (Oscilloscope not
included.)

Paper Tape and Card Equipment
CAWO READER ANP CON?l?Ol.n
YWE 41
Operates at a rate of up to 200 cards per minute. Cards are read column by column. Column
information may be read in alphanumeric or
binary mode. The alphanumeric mode converts
the 12-bit Hollerith Code of one column into the
6-bit binary-coded decimal code with code validity checking. The binary mode reads a 12-bit
column directly into the PDP-4. Approximately
one per cent of a Card Reader program running
time is required to read the 80 columns of information at the 200 cards per minute rate.

CW4D PUNCH QIDNJaOL-TVPE 40
Enables the operation of a standard IBM Type
523 Summary Punch with PDP-4. Cards are
punched row by row at a rate of 100 cards per

minute. Approximately 0.3 per cent of program
running time is required to operate the Card
Punch at the 100-card-per-minute rate. Buffer
holds one 80-bit row.

MuR~TED
T . PUNCH AN8
COWRETL-TYPE 75
The Type 75 is a Teletype BRPE Punch with an
operating speed of 63.3 lines or characters per
second. It punches 5, 7 or 8-hole tape. (Shown
with Standard Perforated Tape Reader.)

Printers
.

AUl'OMbTlC UNE PRJNER AND
CONTROL-WPE 8rE
Prints 300 lines per minute, 120 columns per
line, 64 characters per column.

PRINTER-KEYBOARD AND CONTROL
TYPE 65

The Type 65 is a Teletype Model KSR-28 Printer
and Keyboard with an input and printing speed
of 10 characters per second.

Magnetic Tape Equipment
MAGNETIC TAPE TRANSPOW
TYPE S f B
Controls a maximum of eight tape transports
automatically. Provides information transfer
through computer's data interrupt facility. Controls reading or writing of tape at various rates
compatible with IBM, BCD or binary parity
modes.
The Type 57A can be used in conjunction with
one of the following interfaces.
Tape Control lnterface Type 520 - permits
attachment of the Type 50 Tape Transport.
Tape Control lnterface Type 521 - permits
attachment of the Type 570 Tape Transport.
Tape Control lnterface Type 522 - permits
attachment for one of the following type
transports: IBM series 729 model II, IV,
V, VI or IBM series 7330. Character transfer capabilities of 7.2 to 90 KC at densities
of 200, 556, and 800.

MAGNETIC TAPE CQNTNL-WPE 54
Controls up to four Magnetic Tape Transpofl
Units, Type 50. Information is read from or
written on the tape under program control.
Subroutines are available to read and write IBM
compatible tapes having a density of 200, 6
1 bit characters per inch.

Reads and writes IBM formats on 1/2 inch
tape at transfer rates from 15 to 62.5 KC.
Tape speed is 75 or 112.5 ips with densities
of 200 or 556 bits per inch. The transport
has optional capability for multiplexed time
shared operation.

MAQffEflC TAPE TRAMPORT
TYPE 459

Used wieh Type 54 and Type 57A controls.
Transfers from 1 to 15,000 characters per second on 1/2 inch tape at a speed of 75 inches per

second. The number of characters per inch is
variable from 1 to 200; the number of bits per
character is 7.

MICRO TAPE DUAL TAPE TRANSPORT
AND CONTROL TYPE 565-550
Fixed address magnetic tape for high speed

loading and readout as well as program updating. Two logically independent tape drives handle 260 foot pocket-size reels of 3/4 inch Mylar
tape at a speed of 8 0 inches per second. fnformation is written on non-adjacent, redundant

tracks in the Phase Recording System at densities of 375 bits per track inch and may be transferred at a rate of 90,000 bits per second. Tape
handling and utility transfer routines available.

In-Out Connections and Controls
fer between the computer and external devices
10-BIT OUTPUT RELAY BUFFER at word rates t o 125 KC.
TYPE 140
Provides contacts whicl Operate devices of
CLOCK Y ULtlPCDlER - WPE 132
"D"
higher power rating. The relays
have

Provides 16 inputs to the PDP-4 enabling 16
contacts, which open and closein approximately memory registers to be used as 18-bit counter.
3 milliseconds,
Priority addressing system permits combined

I1JTeRFACE FOR lBMl7OgO
CONNECTION TYPE 156

Provides communication between PDP-4 and
IBM 7090 at a 10,000 cps, 18-bit word rate.

DATA CONTROL

- TYPE 131

Controls and double buffers high speed trans-

input counting rate to 125,000 cps.

DATA IN1ERRUPT MULTIPLEXER
TYPE 133

Provides high-speed transfer between PDP-4
Core Memory and three input-output devices.
Maximum combined transfer rate: 125,000 c ~ s ,
18-bit words.

Analog-to-Digital Equipment
GENERAL PURPOSE N & O G TO
DIGITAL CONVERTER TYPE f 38

HIGH SPEED ANALOG TO DIGITAL
CONVERTER- TYPE 142

A general purpose analog t o digital converter
used to convert input analog voltages into digital numbers for computer entry.

Converts analog signals to digital information
with 10-bit accuracies in 8 microseconds for
computer entry.

GENERAL PURPOSE 64 CHANNEL
MULTIPLEXER CONTROL- TYPE 139

HlGH SPEED MULTIPLEXER CDN

Controls up to 6 4 channels of analog input t o
be multiplexed into the analog to digital converter.

High speed multiplexer for use with the Type
142 Analog to Digital Converter.

TROt TYPE 141

Special purpose analog to digltal converters, multiplexers, multiplex switches, digital to
analog converters, plotters and loggers w ~ t hvarious speeds, accuracies, and Input ranges
are available for special requirements.

PROGRAMMING
The PDP-4 instruction format includes 4 bits for
instruction code, 1 bit for indirect modified addressing and 13 bits for memory address or
variations of the basic instructions.

Code

Llndirect Bit

Operand Address

When the indirect bit is a ONE, indirect addressing (or deferring) is specified. A defer memory
cycle is required during which time the contents
of the memory cell addressed are selected and
the address part of this cell is used as the effective address of the original instruction. The
instruction part of the cell and the indirect bit
are ignored when obtaining the effective address. In addition, if the cell indirectly addressed
is 108-178, a ONE is added to the contents of
that cell before the address part is used as the
effective address (auto-indexing).
Operating times of PDP-4 instructions are in
multiples of the 8 microsecond memory cycle.
Add, deposit, and load for example, are twocycle instructions completed in 16 microseconds. Input-output connections are programmed
by specifying iot instructions which affect the
state of selected devices. The instructions may
be microprogrammed to allow one basic instruction t o handle one or more devices by changing
the bits of the command.

Exclusive OR, The excluralvs "OR"
logicerl fu~ctionis pertermed on a
bit-bybit baais betwefan the CCAC)
and CCfj. The result is left in the
A6 and the originrt CCAC) are lost

IN-OUT TRANSFER GROUP
ctions in this group are similar to the Operatl
ructions except they pertain to the transfer of in
between the Central Processor and various inpul
ctions provide micro pr
Operation

iot

7Oxxxx

Keys and toggle switches available on the
PDP-4 control panel provide maximum ease of
operation. Their functions are as follows:

Console Keys
START
Starts the processor. The first instruction is
taken from memory cell specified by the setting
of the ADDRESS switches. The START operation
clears the AC and Link, and turns off the Program Interrupt.

STOP
Causes the processor to halt functional operations at the completion of the memory cycle in
progress at the time of key operation.

CONTINUE
Causes the processor to resume operation beginning at the address specified by the Program
Counter (PC).

EXAMINE
Sets the contents of the memory location indicated by the Address Switches into the Accumulator (AC) and Memory Buffer.
he Memory Address Register will contain the
address of the memory location being examined and the program counter will contain the
address of the next location.

DEPOSIT
Sets the word selected by the Accumulator
Switches (ACS) into the memory at the location
specified by the Address Switches. The results
will remain in the Accumulator and the Memory
Buffer. The Memory Address Register will contain the address of the memory location holding
the information, and the Program Counter will
contain the address of the next location.

EXAMINE NEXT
Sets the contents of the memory at the address
specified by the Program Counter into the Accumulator and the Memory Buffer. The C(PC)
are indexed by one, and the Memory Address
Register will contain the address of the location
examined.

DEPOSIT NEXT
Sets the contents of the Accumulator Switches
into the memory at the location specified by the
Program Counter. The C(PC) will be indexed
by one, and the Memory Address Register will
contain the address of the location holding the
information.

Console Toggle Switchee
POWER
Turns on the power.

SINGLE STEP
Causes the processor to halt at the completion
of each memory cycle. This switch is particularly useful in maintenance tasks. Repeated
operation of the Continue Key will step the program one cycle at a time so that the state of
the machine can be examined at each step.

SINGLE INSTRUCTION
Causes the processor to stop at the completion
of each instruction.

REPEAT
Causes operations initiated by console keys to
be repeated as long as the keys are depressed.
The operations are performed at the rate set
by the Speed Switch.

SPEED
Controls the speed of the repeat function.

PROGRAMMING AIDS
The PDP-4 Programming System includes FORTRAN 11, a Symbolic Assembly
and Debugging System, maintenance routines, and numerous other programming aids.

FORTRAN II
PDP-4 FORTRAN 11 allows the programmer an
unusual degree of freedom in many instances:
For example, mixed expressions and n-dimensional arrays are allowed. An important feature
is the retention of the original symbols from the
FORTRAN source language tape through the

final binary program, making the system easy
to Use and reducing debugging time. COm~ilation of the original FORTRAN source program
is performed alone, with subprograms compiled
and assembled separately. Hence, should mistakes occur in FORTRAN coding, only the main
program need be recompiled.

POP-FORT

1-6 decimal digits absolute value 5 131,071
FLOATING POINT
RIABLE NAMES:

10 decimal digits precision. Exponent range 2(217-1)
t0--2(2~7-1)

1-6 alphanumeric characters
Any arithmetic expression representing an integer
quantity: Variables in a subscript may themselves be
subscripted to any depth. N dimensional arrays are
permitted.

STATEMENTS:

Mixed expressions containing both fixed and floating
point variables are permitted. A maximum of 300
characters are allowed (statement numbers not
counted)

STATEMENT
NUMBERS:
FUNCTIONS AND
SUBROUTINES:

Subroutines not contained in the FORTRAN library
may be compiled by the use of Function and Subroutine statements. Functions and subroutines may
be fixed or floating point valued as defined by initial
letter of F-type function convention. Arguments
may be arbitrary arithmetic expressions, including
functions.
MICRO-TAPE, paper tape, punched cards, teletype,
display. Format may be specified by use of a
FORMAT statement.

STATEMENTS
AVAILABLE:

Arithmetic statements, 1/0 statements with FORMAT,
DO, Dimension, Common, IF, GOTO, Assign, Continue, Call, Subroutine, Function, Return.

Symbolic Assembly and
Debugging System
ASSEMBLY PROGRAM

DDT-4 (DEC DEBUGGING TAPE-4)

A one-pass assembler that allows mnemonic
symbols to be used for addresses and instructions. Constant and variable storage registers
are automatically assigned. This assembler will
produce relocatable or absolute binary output,
as desired by the user.

Debugging may be done at run time using the
teleprinter. Break points may be inserted into
a program at arbitrary points so that the state
and operation of a program may be observed.
The source program symbols may be used for
communication.

RELOCATING LOADER
Performs relocation and linking of binary programs that have been assembled separately.

EDMUND THE EDITOR
Allows the editing of symbolic tapes.

Arithmetic Routines
DOUBLE PRECISION
INTEGER PACKAGE
A collection of subroutines which allow the user
to perform double precision arithmetic with
35-bit signed numbers.

MULTIPLY AND DIVIDE SUBROUTINES
Single precision signed one's complement.

DOUBLE PRECISION FLOATING
POINT
Performs operations upon floating point numbers, with approximately 10 decimal digits of

precision, and an exponent which may be as
large as 2(*17-1)in magnitude.

AUTOMATIC MULTIPLY AND DIVIDE
Provided by the Extended Arithmetic Element
Type 18, also includes shift and normalize functions permitting fast floating point operations.

STANDARD FUNCTION GENERATORS
Routines to calculate floating point, arctan (x),
sin (x), cos (x), e; log (x), xy, 6.

I10 Programs
MAGNETIC TAPE PACKAGE

PEN FOLLOW

Facilitates use of Type 57A and Type 54 Control units.

Tracks the light pen across the face of the
Type 30 Precision CRT Display.

MICRO TAPE PACKAGE

BUFFERED I/O PACKAGE

For use with Micro Tape 555.

SYMBOL GENERATOR ROUTINES
A high speed plotting routine for use with the
Type 33 Symbol Generator.

Permits simultaneous use of the paper tape
reader, paper tape punch, card reader, card
punch, high speed line printer, teleprinter and
keyboard, buffering all input and output.

Utility Routines
Facilitates the calling of subroutines. Permits
greater freedom in the use of subroutines, including recursive calls.

Allow punching in either block format binary or
read-in mode format.

M A S m TAPE DUPLIOATOW
Verifies and duplicates tapes.

Maintenance Routines
Many of these maintenance routines are also
used on DEC's standard acceptance tests. Special I/O test programs are available as required.

CamEST
(Continuous Test) Repeatedly tests all basic
machine functions.

MMNDEC 401 INSTRUCTIOM TEST
A sequence of programs which test the operation of all PDP-4 instructions except the iot
group.

HAINE)E:G402 CHECKER@O&RD
Provides continuous memory testing with four
different patterns.

IUAIN@EC403 ADDRESS SET
Maintenance programs to check the memory
module for proper address selection.

m uANb PUNCH TEST
Checks the operation of the reader and punch
using different patterns and variable times.

lE.LEpRIIYTER E S T
Tests the input and output facilities of the teleprinter by repeating the typed message, echo
checking, etc.

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