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XX-75E55-E9

July 1965

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6.9MB

Document:	F-61 PDP-6 Brochure
Order Number:	XX-75E55-E9
Revision:
Pages:	13
Original Filename:	http://bitsavers.org/pdf/dec/pdp6/F-61_PDP-6_Brochure_Jul65.pdf

OCR Text

FROGRAMMED DATA FROCESSOR-8

36-bit word length _ 15 index registers and/or accumulators FORTRAN
" - FORTRAN IV - MACRO-6 assembler - utility programming library
Integrated hardware and software for time sharing _ DECtape
Asynchronous operation, modular construction _ Memory overlap
Core memories up to 262,144 words, 1.75 fJ-sec, directly addressable
Fast memory 16 words, 0.4 microsecond _ 128 input-output devices
363 instructions _ fast floating point multiply 20 fJ-sec average
Program assignable operation codes _ Byte manipulation , half word
Block transmission _ Seven channel priority interrupt system
Programmed input ·output transfers require no data channels
Multiple processors _ Remote input -output _ Mass memory

Programmed Data Processor·6 (PDP·6) is a general·
purpose digital computing system designed for large·
scale scientific data processing. The flexibility of
this system permits the user to specify the data
handling capacity and the exact configuration needed
to meet his requirements. The system can be ex·
panded with presently available equipment or, at a
later date, with equipment yet to be developed.
Faster memories, for example, can be added as they
become available.

Neither the processors nor any of the standard
peripheral equipment require floor reinforcement.
Ordinary 115 · volt power is sufficient for all
equipment.

PDp·6 design eliminates the need for off·line con·
version equipment. Conversion of programs from
cards or paper tape to magnetic tape can be done
concurrent with normal program running. Users at
peripheral Teleprinters can simultaneously prepare
and debug their programs on line.

The Type 166 is a 36·bit arithmetic processor with
many powerful features, including 16 accumulators,
15 index registers, built·in floating point arithmetic,
and byte operations capability. Memory protection
and relocation registers are included for time·shar·
ing operations.

The PDp·6 system consists of processors, memories,
and input/ output devices. Since each is autonomous
(no device is dependent upon another for its timing) ,
a system configuration can include memory modules
of different speeds, processors of different types
sharing the same memory modules, and standard or
unique input/ output devices.

The Drum Processor gives direct memory access to
high speed mass storage files. It takes over local
control of data transfers after receiving system com·
mands and initial conditions from the arithmetic
processor. Thereafter the two processors operate
asynchronously, so that I/O transfers are carried
out in parallel with arithmetic processing. Up to four
mass storage files may be connected to the Drum
Processor.

For maximum flexibility of system configurations,
the PDP·6 system is built around two busses: proc·
essor·memory bus and processor·input/ output bus.
The memory bus permits each processor to directly
address 262,144 words of core memory, automati ·
cally permits overlapping, and simplifies multiproc·
essor operation. An input/ output bus of processor
can service up to 128 devices.
The Operating System consists of a supervisory con·
trol program , system programs, and system sub·
routines . Included are a Symbolic Assembler and
Macro Processor, FORTRAN II and FORTRAN IV
Compilers, and debugging aids. A library of general
utility programs is also provided.

PROCESSORS
A PDp·6 system can include any number of proces·
sors of the same or different types.

INPUT /OUTPUT
The input/ output bus consists of device selection,
data, control, and status sense lines. A seven·chan ·
nel program·assignable priority interrupt system
signals the processor when input/ output devices
require service. Word count and memory address
registers are located in the processor and are avail ·
able to all devices. This reduces the cost of various
input/ output controls, and permits data block trans·
fers between tapes, card readers , printers, displays,
and other devices.

MEMORY
The PDP-6 core memory subsystem permits modular expansion using blocks of different sizes and
speeds. The Type 163C core memory module contains 16,384 words. The Type 164E memory module
contains 65,536 words. Each has a word length of
36 bits, a cycle time of 1.75 microseconds, and an
access time of 0.95 microseconds. The Type 162
Fast Memory Module contains 16 words with a 004microsecond cycle. Slower core memories, such as
the 5-microsecond Type 161, can be used where
economy is an overriding criterion.
The memory-processor bus permits memory cycle
overlap, gives all processors direct access to memory,
and permits easy expansion and modification of the
memory subsystem. In addition, the bus allows the
processors to remain connected to memory only as
long as needed to transfer information: That is, a
processor can put a word on the bus and resume
operations as soon as the memory acknowledges,

without waiting for the memory to store the word.
Similarly, when reading a word out of memory, the
processor takes the information and operates on it
immediately, without waiting for the memory to
finish the rewrite portion of its cycle.
Maximum system efficiency is achieved when sequential memory references address alternate memory modules. The addressed module places data on
the bus as soon as it is available in the memory
buffer and disconnects itself from the bus while
rewriting, freeing the processor to store the result
or seek the next instruction in a second memory
module before the first one has completed rewriting.
Utilizing such overlapping memory references,
PDP-6 users can effectively cut in half the time required for average random accesses. Multiple connections between the bus and each memory module
permit module sharing on a priority basis for multiprocessor operations.

The programming system for PDP-6 consists of a
supervisory control program, system programs, and
library routines. The entire system is designed to
run on any PDP-6 system with at least 16,384 words
of core memory, a console Teleprinter, and a
DECtape system. The supervisory control program or
monitor is designed specifically to allow many users
to time share the central processor. All common
user service programs are also written to be run by
multiple users in a time-shared environment.
A more detailed study of the time-sharing software
developed for PDP-6 is contained in DEC brochure
F61B, "PDP-6 Time Sharing Software."
A variety of programs are provided through the
Digital program library, and a continuous in-house
program design effort regularly improves and expands the library.

THE SUPERVISORY CONTROL PROGRAM
This is the name given to a collection of programs
remaining permanently in memory to provide overall
coordination and control of the total operating sys·
tem . The segments of the program are:
Command Control Program, which handles all com mands addressed to the system from the User-Con soles. These commands include requests to log in
or out, a request to use the edit program, requests
to have a program placed on the run queue, requests
to load a program, etc .
Program Scheduler, which is called at regular intervals to decide which program in memory is to be
run. A running program is temporarily terminated
each time its allotted time has run out, or when it
requires input-output operations with a device that
is busy. A program may be terminated temporarily
by user intervention to the scheduler, or it may suspend its own operation . Temporary termination does
not remove the program from memory. A program

may be dumped on backing storage and permanently
discontinued by calling the scheduler and allocator.
Facilities Allocator, which is called any time an I/ O
device or memory space is required. It may be called
from a User-Console or by a running program. Under
this program one User-Console is designated the
operator console. As such it has special facilities
available which are not available to other consoles,
such as line printer assignments. Storage is permanently assigned for all resident programs, that is,
those programs that are in memory at all times.
Finally, "logical" tape assignments are made. Two
DECtape units are designated the system library
and the system scratch tape. Two other tapes may
be assigned as Peripheral Input Tape, used to prePClre jobs to be stacked from cards or paper tape,
and System Input Tape, used to input a full tape.
(Each User-Console may require a DECtape unless
programs requiring files are to be run .)
I/ O Control is called whenever an I/ O device is to be
used . This program assigns equipment, controls the
I/ O devices, controls data transfers between memory
and the I/ O device, and controls the buffering of
data for the device . (Users provide the necessary
buffering for devices which require file buffering.)
All program I/ O instructions are trapped, and the
actual control of the I/ O operation then passes to
the I/ O Control Program.

COMMON USER SERVICE PROGRAMS
These are the programs designed to implement system functions which may be requested from the
User-Console. This is in contrast to system subroutines which may be called by system programs
or other programs . Common user service programs
are normally provided by Digital, but they may be
provided by each installation for its users. The programs contain a mode by which they may be ter ·

minated to return the communication link to the
system . Some of the system programs are described
below.
Editor Program, which provides a means for manipulating the text of a named file on a DECtape or
in the user area of the drum (corresponding to DECTape). This file may be used for the creation of text
or for later use as data or as a program to be translated by the FORTRAN compiler, etc. The commands
provided for the editor allow text to be created . deleted, or moved about .
Peripheral Interchange Program, which handles all
those jobs normally done by a separate peripheral
processor. The priority interrupt system and multiple
memory accumulators in the PDP-6 eliminate virtually all loss in running time. Such processing is done
through the arithmetic processor.
Linking Loader Program accepts programs in a form

produced by the translators. and produces an area of
core memory loaded with the program. Upon request.
it may also produce a storage map of the loaded
programs along with symbol tables. Several programs
may be linked together in loading. The loader requests special library tapes to be loaded. and verifies
that the program has been completely loaded .

octal . decimal. and floating point. Text may be placed
in a binary program by the occurrence of the "text"
data generating statement, and "byte" will cause a
string of bytes to be assigned and packed into a
word. The " repeat " control statement causes the
statements following the control to be repeated "n"
times.
Debugging Program (DDT) is loaded with a program
and allows all assembly language programs to be
debugged . The program may be started or stopped.
words in the program may be modified, and DDT
may search the program looking for particular words.
DDT may also be used in a " trace" or break point
mode, and the program is run until a particular location (a break point) is encountered.
The System Subroutines include:

1. I/ O Format Control which provides for the various
format statements used in the FORTRAN languages . These subroutines are also available to
other programs and may be called from the systems library tape.
2. Arithmetic Subroutines which include all the arithmetic subroutines required for FORTRAN. such
as. sine. cosine. loge. log lo. exponent. tangent.
arc-tangent. and square root.

FORTRAN IV Compiler accepts FORTRAN IV source
statements and produces relocatable binary output.
Compilation is completed in one-pass at approximately 2000 statements per minute. A unique feature of this compiler is that it may be run
concurrently by several users . After initially loading
FORTRAN IV. the monitor will direct additional requests to the copy already residing in core. Each
additional user requires only a small amount of
temporary storage.
FORTRAN /I Compiler accepts FORTRAN II source

statements and produces relocatable binary output
for later loading by the Linking Loader. Compiling is
done in one pass. PDP-6 FORTRAN II is an exten sion of the conventional FORTRAN II language to
give the user more facilities and to take advantage
of PDP-6 hardware. The ASCII character set is used.
Subscripts may consist of statements (fixed or floating). Any number of dimensions may be used to
specify an array. Signed integers have 36-bit values,
but when used as subscripts are truncated to 18 bits.
MACRO-6 Assembly Program translates MACRO-6

input language to a relocatable binary output for the
Linking Loader. MACRO-6 is a two-pass assembly
program and the language provides for instruction
definitions and usage. Literal assignments are made
by brackets []. Numbers may be expressed as binary,
7

MEMORY
MODULE

f- f-

ARITHMETIC
PROCESSOR
166

PERFORATED
TAPE
READER
760

PERFORATED
TAPE
PUNCH
761

TELEPRINTER
CONTROL
626

CARD
READER
461

CARD
PUNCH
460

LINE
PRINTER
646C

DATA
COMM
SYSTEM
630

DISPLAY
CONTROL
AND
MONITOR
346

MAGNETIC
TAPE
CONTROL
516

H
MEMORY
MODULE

f- H

400 CPS
READER

MEMORY
MODULE

63 .3 CPS
PUNCH

CONSOLE
TELEPRINTER

200/800
CPM
READER

100/300
CPM
PUNCH

DATA
CONTROL
136

DECTAPE
CONTROL
551

DISC
FILE
CONTROL

MONITOR .......
343

TRANS
570

TRANS ~
555

DISC
FILE
270

TTY
LINE

MONITOR .......
343

TRANS
570

TRANS ---<
555

DISC
FILE
270

1000 LPM
PRINTER

I
"-

DATA
CONTROL
136

H
f- H

UP TO

DRUM
PROCESSOR

•
•

I I I I
I I I I

•
H

DRUM

I-<

DRUM

I-<

DRUM

I-<

DRUM

FDF-E3-A MODULAR SYSTEM

I- H

rMEMORY
MODULE

TTY
LINE

UP TO
64

MEMORY
MODULE

f--

TO
OTHER
PROCESSORS

_ _ -.J

- - - ...J

The diagram shows the three main parts of a PDP-6
system memories, processors, and input-output
equipment - interconnected with busses. Memories
and input-output devices contain their own buffer
registers and control circuits, including decoders to
recognize commands from the processors. The Data
Control Type 136 is a double-buffered device which
is used not only with magnetic tape equipment, as
shown here, but with any high speed, block transfer
device, such as drum or disc.
The system shown in this diagram is a theoretical
one of very high capacity, but it is entirely within
the capability of PDP-6. Memory size, indicated by
the modules on the left, can be as large as 262,144
words per processor, and up to four processors can
address a given memory module. Up to four mass
storage files can have direct access to the memory
system through the Drum Processor, The combination of the asynchronous nature of the system and

the characteristics of the memory bus makes possible truly simultaneous memory references by two
or more processors. Sequential memory references
made by one processor can be overlapped.
PDP-6 is also a highly effective system in a minimum
configuration. All system programs will operate in a
system consisting of a Type 166 Arithmetic Processor,
a Memory Module of 16,384 words, a DECtape system, and a Teleprinter. Later expansion of either the
memory or input-output system can be made with no
change whatever in the existing system. Memory
modules can be of any speed: A low cost system
might call initially for slower (5-microsecond) memories, later to be augmented by faster memories
(down to O.5-microsecond).
PDP-6 systems are thus completely adaptable to current and future requirements, both technical and
budgetary.

10
11

INSTRUCTIONS
Average
Instruction Times

No. of Instructions
Instructions

The Type 166 Arithmetic Processor is a general purpose processor capable of performing arithmetic,
logical and input/ output operations. It uses the first
16 locations in memory as accumulators, index registers, or ordinary memory locations. The results of
each operation are transmitted automatically to one
of these registers at the end of each instruction ; thus
the accumulator resides in memory.
Executive mode hardware is provided for time sharing. Programs to be run are placed in memory and
relocated by the Relocation Register. Memory references outside of the area assigned to the user are
detected by the Memory Protection Register, and a
supervisory program is called to check for the cause
of the illegal reference . In addition to this specific
hardware, PDP-6 time-sharing capabil ity is further
enhanced by the processor' s ability to address up to
262 ,144 words of memory directly and by the uni form representation of program symbols in ASCII
code.
The 363 operation codes include fixed and floating
point arithmetic, logical or Boolean , memory or ac-

cumulator modification and testing, half word, vari able sized byte, block transmission, and input-output
instructions. Instruction times vary, depending on the
memory subsystem selected . Use of the Type 162
Fast Memory reduces instruction times significantly.
The table (right) shows the number and kind of
instructions and their typical speed of execution.
Times are based on the instruction and data located
in non -overlapped 1.75 p's memory with accumu lators located in 400 nanosecond fast memory in
executive mode . Arithmetic speeds are averaged
using random numbers. The times are not necessarily minimum since factors such as memory overlapping, execution in fast memory, immediate mode
operations and other factors are not considered.
Nor are they maximum times, since an instruction
may take cons iderably longer if there are several
levels of indirect addressing. Exact t imes depend
on the program context in which the instructions
occur and on other factors ; therefore the figures
should not be used to calculate program running
time.

Modes

Full word moves
Half word moves
Byte manipulation
Block transfer
Exchange

4
16
5
1
1

4
4

16
64
5
1
1

4.0 p'sec
4.0
8.5
2 + 4 n
4.2

Fixed point add
Fixed point subtract
Fixed point multiply
Fixed point divide

1
1
2
2

4
4
4
4

4
4
8
8

4.4
4.6
20.0
28.0

Floating point add
Floating point subtract
Floating point multiply
Floating point divide

2
2
2, 1
2

4
4
4
4

8
8
9
8

9.3
9.9
20.0
27.0

Boolean

4.1

Shifting (18 bits)

5.9

Memory, AC modification and testing
Arithmetic compare
Logical compare
Jumping

6
2
16
8

I/ O
basic
augmented

Push down

[ III i

t' '0 ' ' I t U

STAT

.'110....

4
4

6.2
8.1

6.4

~ HOutS'

PI t.CTIV[

AIIOAUS

IUD

4
4

(11)(11)[11)(11]

DAti

3.9
4.9
3 _9
2.9

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C •••••••
c •••••••

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t I I It i i if I I It I I lt lilt I I it I I ][ I I j[ t I it I I i

48
16
64
8

8
8
4

M( M STOfl'

Fast

Total
Instructions

Operations

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Digital offers a large selection of optional equipment
for full utilization of the extensive input/ output
capacity of the system.
DECTAPE TRANSPORT TYPE 555
A fixed address magnetic tape facility for high speed
loading, readout, and on-line program debugging.
Read, write, and search speed is 80 inches a second.
Density is 375 bits an inch. Total storage is three
million bits. Features phase recording, rather than
amplitude recording; redundant, nonadjacent data
tracks, and a pre-recorded timing and mark track.
DECTAPE CONTROL TYPE 551
Controls up to eight Type 555 DEC-tape Transports. Searches in either direction for specified block
numbers, then reads or writes data. Uses the Type
136 Data Control to assemble data and buffer transfers to the processor.
DATA CONTROL TYPE 136
Provides for assembly of 6, 12, 18, or 36-bit characters; six input/output devices can be controlled.
TELEPRINTER AND CONTROL TYPE 626
Permits on-line programming and debugging. Pro·
vides hardcopy outputs. Is standard Teletype equip·
ment, operating at ten characters a second. Included
with Arithmetic Process<;>r Type 166.
DATA COMMUNICATION SYSTEM TYPE 630
Automatically scans up to 64 teleprinter (TTY) lines.
Signals a program interrupt when teleprinter needs
service.
HIGH SPEED PERFORATED TAPE PUNCH
AND CONTROL TYPE 761
Punches 8-hole tape at 63.3 characters a second .
HIGH SPEED PERFORATED TAPE READER
AND CONTROL TYPE 760
Reads perforated paper tape photo-electrically at

400-characters a second. Included with Arithmetic
Processor Type 166.
AUTOMATIC LINE PRINTER AND CONTROL
TYPE 646 A, B, C
Prints 300, 600, or 1000 lines a minute, 120 columns a line, anyone of 64 characters a column. Also
available with 132 columns a line.
CARD READER AND CONTROL TYPE 461 A, B
Provides on-line reading of standard punched cards
at 200 or 800 cards a minute in alphanumeric or
binary codes.
MAGNETIC TAPE CONTROL TYPE 516
Automatically controls up to eight tape transports
Type 570 or IBM 729 series. Perrnits reading, writing, forward / backward spacing, rewind and unload,
and rewind. Uses a Type 136 Data Control to assemble data and buffer transfers to the processor. longitudinal and lateral parity is checked.
MAGNETIC TAPE TRANSPORT TYPE 570
Tape motion is controlled by pneumatic capstans
and brakes, eliminating conventional pinch rollers,
clamps, and mechanical arms . Tape speed is either
75 or 112.5 inches a second . Track density, program-selectable, is 200,556 ,and 800 bits an inch.
Tape width is one-half inch, with six data tracks and
one for parity. Format is compatible with IBM NRZI.
Dual heads permit read checking while writing.
DRUM PROCESSOR TYPE 167
Establishes a data transmission path between main
memory and up to four magnetic drum storage units.
ANAlOG-TO-DIGITAl CONVERTER TYPE 138
Transforms an analog voltage to a binary number,
relectable from six to eleven bits. Conversion time

varies, depending on the number of bits and the accuracy required. Twenty-one combinations of switching point accuracy and number of bits can be selected
on the front panel.

DISC FILE AND CONTROL
TYPE 270
Each disc file stores a total of 5.76 million 36-bit
words. Transfer rates are 51.8 p.sec/word outer zone,
88.8 p.sec/word inner zone. Average access time is
190 msec.

DISPLAY CONTROL AND MONITOR TYPE 346
Plots points, lines, vectors, and characters on a
9%-inch -square raster of 1,024 points along each
axis. Time between points plotted is 1.5 microseconds in the vector, increment, and character
modes. In random point plotting, a time of about 35
microseconds is required per point.

Four different calcomp plotter models may be in terfaced directly to the I/O bus or via the 630 data
communication system.

DISPLAY MONITOR TYPE 343
Provides additional cathode ray tube display for multiple consoles.

MULTIPLE COMPUTER
INTERCOMMUNICATION SYSTEM
TYPE 165

HIGH SPEED LIGHT PEN TYPE 370
Detects data displayed by the Types 346 and 343
and inputs identifying signal to the computer.

The Type 165 provides a data intercommunication
path between PDP-6 Arithmetic Processors/Memories and up to eight PDP-7 or PDP-8 computers.

CALCOMP PLOTTERS
TYPES 653 -566

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15017

PRINTED IN U.S.A.

25-7/ 65