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         ORDVAC Ordnance Variable Automatic Computer (U.S. Army Photo)

APPLICATIONS (Ballistic Research Laboratories)

Exterior ballistics problems such as high altitudes, solar and lunar trajectories, computation for the preparation of firing tables and guidance control data for Ordnance weapons, including free flight and guided missiles.

Interior ballistic problems, including projectile, propellant, and launcher behavior, e.g., physical characteristics of solid propellants, equilibrium composition and thermodynamic properties of rocket propellants, computation of detonation waves for reflected shock waves, vibration of gun barrels and the flow of fluids in porous media.

Terminal ballistic problems, including nuclear, fragmentation and penetration effects in such areas as explosion kinetics, shaped charge behavior, ignition, and heat transfer.

Ballistic measurement problems, including photogrammetric, ionospheric, and damping of satellite spin calculations, reduction of satellite doppler tracking data, and computation of satellite orbital elements.

Weapon systems evaluation problems, including anti-aircraft and anti- missile evaluation, war game problems, linear programming for solution of Army logistical problems, probabilities of mine detonations, and lethal area and kill probabilities of mine detonations, and lethal area and kill probability studies of missiles.

Transistorized Arithmetic Unit (U.S. Army Photo)


Internal number system                         Binary
Binary digits per word                             40
Instructions per word                               2
Instruction type                          One Address
Binary digits in operation code                6 or 9
Binary digits in address                     12 or 10
Instructions used                            55 or 72
Arithmetic system                         Fixed point
Number range               -1 less than x less than 1

Instruction word format
   Left Instruction           Right Instruction
  6       2       12          6       2       12
Order  Unused*  Address     Order   Unused*  Address
       20 Bits                      20 Bits

*One bit will be used to differentiate floating point numbers from fix point numbers

Rapid Access word registers - 3
Sexadecimal representation is used externally.
Negative numbers are handled as 2 complements.
Floating point operation may be programmed.

Dual code - ORDVAC operates on a dual code basis.  The codes are, on a two
instructions per word basis, i.e., 20 digits per instruction:

Code A - 1,024 words of storage:
  9 digit, command
  1 digit, spare
 10 digit, address
Code B - 4,096 words of storage:
  6 digit, command
  2 digit, spare
 12 digit, address

This system permits utilization of routines developed previous to the 4,096-
word operation change over.
Magnetic core memory (U.S. Army Photo)


Arithmetic mode                                  Parallel
Basic pulse rate                                 Not pulse controlled
Add time (basic addition by arithmetic unit)     14 microsec
Multiply time (exclud. stor. access)            700 microsec
Divide time (exclud. stor. access)              700 microsec

The total add time, including transfer to final register, is 50 microseconds. None of the above figures include access to storage.

Construction, Arithmetic unit only - Transistorized on printed circuit plug-in boards, using 1,000 Type 2N128 transistors.

Timing         Asynchronous
Operation      Parallel
Transistorized Channel Selector (U.S. Army Photo)


    Media              Words          Digits              Access
Magnetic core          4,096        163,840 bits        15 microsec
Magnetic drum         10,032        401,280 bits        80,000 microsec
                                                        /48 words

Magnetic drum purchased from ERA Division of Sperry Rand, Incorporated. The Track selector for the magnetic drum has been transistorized. Magnetic core storage unit purchased from Telemeter Magnetics, Incorporated. Both above storage units adapted to ORDVAC and installed by Ballistic Research Laboratories personnel.


       Media                           Speed
Teletype tape (5 hole)         2.5 words per sec
Punched cards                 40   words per sec (bin)
                               8   words per sec (dec)
Ferranti Hi-speed Paper
  Tape Reader                   20 words per sec (bin)
Magnetic tape                  300 words per sec

The special purpose one inch wide magnetic tape system for transferring telemetered data to ORDVAC has 6 information tracks and 3 control tracks.


       Media                           Speed
Teletype page printer          0.4 words per sec
Teletype tape                  0.4 words per sec
Punched cards                 40   words per sec (bin)
                               8   words per sec (dec)
Transistorized magnetic core contents display.


Type            Quan                  Type            Quan
5964              817                 C6J              28
5687              420                 6X5               4
2C51              568                 0C3               4
5965              637                 6SF5              4
6AL5               47                 6AC7              4
6A67                2                 12SN7            12
2D21              160                 12AU7             1
6080               21                 6AH6              9
6AN5               13                 6350             86
0B2                14                 6829              2
7AK7               16                 6216              2
5963               46                 6BJ7             42
6AV6               13                 6197             90
5R4                 2                 6293            193
6L6                26                 5998             72
12AX7              22                 6336             27
6X4                 6                 350B              4
5651               12                  0A2              3
6AQ5                1                Total          3,430

Type            Quan                  Type            Quan
2N162              20                 2N1056           250
2N140              65                 2N113             75
2N128           1,300                 2N426             25
2N109             346                 2N425             10
                                      Total          2,091

Type            Quan                  Type            Quan
1N91              418                 1N63              15
1N93              162                 1N58A             10
1N52               10                 1N298            300
                                      Total            915


Power Consumption
      Computer              40 K.W.
      Core Memory           15 K.W.
      Magnetic Drum          6 K.W.

Air Conditioning
    Computer                15 Tons
    Core Memory            7.5 Tons
    Magnetic Drum            3 Tons

    Computer               630 cu ft   80 sp ft

    Computer             3,000 lbs


Number produced to date         1
Number in current operation     1


Rental rates for additional equipment $648.57 per month
The additional rented equipment is:
I.B.M. punch         $ 83.32 per month
I.B.M. reader        $ 82.50
I.B.M. reproducer    $122.50
I.B.M. tabulator     $360.25
Approximate cost of basic system    $600,000.


Typical Personnel
                             Three 8-Hour Shifts
Supervisors                           6
Analysts                              3
Programmers and Coders               14
Clerks                                1
Engineers                             1
Technicians                           6

No engineers are assigned to the operation of the machine, but are used for development and design of additions to the machine. The technicians consult the engineers when a total break-down occurs.


Average error-free running period        Approx. 6 hours
Good-time                                    7,475 hours
Attempted to run time                   8,760 hours/year
Operating ratio                                     0.85

The above figures are based on the yearly average of the last 5 years. Approximately 2 hours per week are used for scheduled preventive maintenance and 10 hours per week are used for running computer test programs. The 1,286 hours difference above were used for testing, servicing, bad operating time, general improvement, and the incorporation of new components.


The ORDVAC belongs to the group of computers whose basic logic was developed by the Institute for Advanced Study and utilized in the IAS computer. This IAS family of computers is made up of such machines as the ILLIAC, ORACLE, AVIDAC, MANIAC, JOHNNIAC, MISTIC, and CYCLONE.

The ORDVAC is a direct-coupled machine using three-dimensional construction. A direct-coupled machine is one that connects the voltage level of one component directly to the input of the next, without voltage isolation between. This feature is very helpful in trouble-shooting the system. Three- dimensional construction is sometimes called low-capacitance wiring. In the ORDVAC, three-dimensional wiring is employed by placing the arithmetic unit and other controls on opposite sides, and interconnected wiring running across the open space between. The machine can be remotely controlled from commercial Teletype units.

ORDVAC is equipped with the option of two different instruction codes. Code -9 (nine bits per instruction) makes 1,024 words of high speed core storage available to the operator while Code -6 (six bits per instruction) makes 4,096 words of high speed storage available. Each code shares a common nine-bit decoder; however, when the code -6 option is used the instruction first passes through a code translator which translates the six bit instruction into its 9-bit equivalent. There is no loss of time while making the code translation.

The translator uses the following number of circuit elements.

  SB 100             135
  2N  43              24
  2N 140              12
  Total              171
Crystal diodes               253
Resistors                    305
Capacitors                    23

The above components are mounted on 21 printed circuit boards. Power dissipation is approximately 5 watts.


     Ballistic Research Laboratories
     Aberdeen Proving Ground, MD


The Floating Point unit for the ORDVAC will be fully transistorized, with a number range of 2^127 to 2^-128, using a seven bit biased exponent. Numbers will be normalized automatically on transfer to storage. The mantissa of the normalized floating-point number will have a range of 1/2 greater than c greater than -1/2. This system will require that an existing register be converted from a one-sided shifting register to a two-sided shifting register.

Fully transistorized control circuitry for new indexing orders will be added in the near future.

General purpose magnetic tape stations will be added to the ORDVAC shortly, with provisions for 8 stations. ORDVAC will control read, write, re- wind forward and backward, move tape forward and back N words, starting at A address of memory, transfer to B address of memory for next instruction, re- record N words, playback N words, check for parity error, transfer on error, and other functions.

Circuit Elements, Entire System

Magnetic Cores
Quan          OD         ID          Thick
172,032      100         70            30   mils
  5,376      375        260           125   mils

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