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ELECTRONIC COMPUTERS WITHIN THE ORDNANCE CORPS

APPENDIX II -- EDVAC

                                     EDVAC

       Electronic Discrete Variable Automatic Computer (U.S. Army Photo)

APPLICATIONS (Ballistic Research Laboratories)

Exterior ballistics problems such as high altitude, 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, was 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.

PROGRAMMING AND NUMERICAL SYSTEM

Internal number system                 Binary
Binary digits per word                   44
Binary digits per instruction        4 bits/command
  10 bits each address
Instruction per word                     1
Instructions decoded                     16
Instruction used                         12
Arithmetic system               Floating and Fixed point
Instruction type                   Four-address code
                    EDVAC Floating Point (U.S. Army Photo)

Number range

Fixed

-(1-2^-43) less than or equal to n less than or equal to (1-2^-43)

Floating

-(1-2^-33)2^511 less than or equal to n less than or equal to (1-2^-33)2^511

The fractional part of floating point number has 33 bits plus sign, and the exponent of 2 may range from -512 to +511.

Instruction word format

Alpha-Add      Beta-Add      Gamma-Add      Delta-Add      Order
  1-10          11-20          21-30          31-40        41-44

ARITHMETIC UNIT

                                        Microsec
Add time (includ. stor. access)             864
  (min 192 max 1,536)
Mult time (includ. stor. access)          2,880
  (min 2,208 max 3,552)
Div time (includ. stor. access)           2,930
  (min 2,256 max 3,600)

Construction                           Vacuum-tubes and Diode-gates
Number of rapid access word registers  4
Basic pulse repetition rate            1.0 megacycle/sec

Arithmetic mode     Serial
Timing              Synchronous
Operation           Sequential

STORAGE

                          Number of          Number of
   Media                    Words             Digits        Access Microsec
Mercury A.D.L.              1,024             48-384             48-384
Magnetic Drum               4,608             48/Word            17,000
  Includes relay hunting and closure.
  The rate of information transfer to and from the drum is at one megacycle
per second.  The block length is optional from 1 to 384 words per transfer
instruction.
Magnetic tape               48/Word
  Maximum number of units that can be connected to the system   7 Units
  Maximum number of characters per linear inch of tape        112 Char/inch
  Channels or tracks on the tape                                8 Track/tape
  Blank tape separating each record                           1.5 Inches
  Tape speed                                                   75 Inches/sec
  Start time                                                    3 Milliseconds
  Stop time                                                     3 Milliseconds
  Average time for experienced operator to change reel of tape 30 Seconds
  Physical properties of tape
    Width                                                     5/8 Inches
    Length of reel                                    1,250/2,500 Feet
    Composition                                               Red Oxide

The magnetic tape system has the following features: Variable block length from 2 to 1,024 words. The search order releases the machine for computation during search. Information which has been taken from a block and operated upon, can be automatically re-recorded in the same block.

INPUT

         Media                                      Speed
Photoelectric Tape Reader                    942 sexadec char/sec
                                              78 words/sec
Card Reader (IBM)                            146 cards/min
                                               8 words/card

OUTPUT

         Media                                      Speed
Paper Tape Perf.                               6 sexadec char/sec
                                              30 words/min
Teletypewriter                                 6 sexadec char/sec
                                              30 words/min
Card Punch                                   125 cards/min
                                           1,000 words/min

CIRCUIT ELEMENTS OF ENTIRE SYSTEM

Type                Quantity             Type              Quantity
Tubes, total                    5,937
6Y6                   1,000              6AN5                 275
6J6                   1,500              2D21                 160
6AG7                  1,127              6SN7                 150
6V6                     900              6AS6                  50
6L6                     275              Misc                 500
Diodes, total                  12,000
1N297                 6,000              Misc               1,200
1N 34                 4,800
Transistors, total                328
2N398                   256              2N123                  4
2N1008B                  60              2N167                  4
2N 43                     4

CHECKING FEATURES

Two arithmetic units perform computation simultaneously, discrepancies halt machine. Unused commands halt machine. Paper tape reader error detection.

POWER, SPACE, WEIGHT, AND SITE PREPARATION

Power, computer                     52 K.W.
Space, computer                    490 sq. ft. floor
Weight, computer                17,300 lbs.
Power, air cond.                    25 K.W.
Space, air cond.                     6 sq. ft. floor
Weight, air cond.                4,345 lbs.
Capacity, air cond                  20 Tons

PRODUCTION RECORD

Number produced                  1
Number in current operation      1

COST, PRICE, AND RENTAL RATES

Approximate cost, basic system            $467,000
Rental rates for additional equipment
  I.B.M.      card reader      $82.50 per month
  I.B.M.      card punch       $93.50 per month

PERSONNEL REQUIREMENTS

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.

RELIABILITY, OPERATING EXPERIENCE, AND TIME AVAILABILITY

Average error-free running time                 Approx. 8 hours
Good time                                       145 hours/week
Attempted to run time                           168 hours/week
Operating ratio                                 0.87

Figures based on last 3 years. The 23 hours per week are devoted to scheduled and unscheduled maintenance, testing, modifications and improvements, time lost due to error, etc. The 145 hours are good, useful production time. EDVAC has been operating since 1949.

ADDITIONAL FEATURES AND REMARKS

INSTALLATIONS

     Ballistic Research Laboratories
     Aberdeen Proving Ground, MD

FUTURE PLANS

A second magnetic drum system, of 16,128 words capacity is being added to the EDVAC. The transistorized track selector will permit channel switching in 48 microseconds. Synchronous Magnetic Drum (U.S. Army Photo)


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