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EDVAC

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Description

The EDVAC is the successor of the ENIAC. Made by the same designers: Mauchly and Eckert.

design by Mauchly and Eckert

This computer was called by acronym EDVAC (Electronic Discrete Variable Automatic Computer) and its public presentation was carried through in 1947

This machine should be abel to hold any programme in memory that was fed to it. This would be possible because EDVAC was going to have more internal memory than any other computing device to date. In other words a multipurpose computer.

The idea being that given a tube of mercury, an electronic pulse could be bounced back and forth to be retrieved at will--another two state device for storing 0s and 1s. This on/off switchability for the memory was required because EDVAC was to use binary rather than decimal numbers, thus simplifying the construction of the arithmetic units.

Specifications

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)

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.

Alpha-Add      Beta-Add      Gamma-Add      Delta-Add      Order

  1-10          11-20          21-30          31-40        41-44

                                        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

                          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.

         Media                                      Speed

Photoelectric Tape Reader                    942 sexadec char/sec

                                              78 words/sec

Card Reader (IBM)                            146 cards/min

                                               8 words/card

         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

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

Chronology

1947 first issue