ENIAC                             World Wide Web

ELECTRONIC COMPUTERS WITHIN THE ORDNANCE CORPS

APPENDIX I -- ENIAC

                                     ENIAC

                             Electronic Numerical
                            Integrator and Computer

                                 MANUFACTURER
                                Moore School of
                            Electrical Engineering
                          University of Pennsylvania

                               OPERATING AGENCY
                           U.S. Army Ordnance Corps
                        Ballistic Research Laboratories
                          Aberdeen Proving Ground, MD

GENERAL SYSTEM

Timing          Synchronous
Operation       Sequential

NUMERICAL SYSTEM

Internal Decimal in basic computer, binary coded decimal in magnetic storage.

Decimal digits per word 10 plus sign
Decimal digits per instruction 2
Instructions per word 5 or 6
Total no. of instructions decoded 100
Total no. of instructions used     97
Arithmetic system          Fixed-point
Instruction type           One-Address Code
Number range      10^-10 -1 to 1-10^-10

ARITHMETIC UNIT

Add time      (excluding storage access)    200 microsec
Multiply time (    "        "       "  )  2,800 microsec
Divide time   (    "        "       "  ) 24,000 microsec
Construction: Vacuum-tubes
Number of rapid access word registers 120
Basic pulse repetition rate  60-125 kilocycles/sec variable.
Arithmetic Mode:   Parallel

Information is transferred in parallel as a serial train of pulses.

STORAGE

                                     Microsec
Media                 Words          Access
Vacuum-tubes             20          200
Magnetic core           100          200
Function table          304          lines of 12 dec
  digits + sign on each constant set-switch
Plug board               96          lines of 12 dec
  digits + sign each (IBM)
Relays                    8          buffer capable
  of storing contents of one card

INPUT

Media                 Speed
IBM Cards         125 cards/min

Each card has 8 ten decimal digit words plus signs.

OUTPUT

Media                 Speed
IBM Cards         100 cards/min

200 millisec of card cycle are available for other computer operations. At 50 cards/min rate, 800 millisec are available for computer operations per card cycle.

NUMBER OF CIRCUIT ELEMENTS

Tubes                       17,468
Tube types                      16
Crystal diodes               7,200
Magnetic elements            4,100

PHYSICAL FACTORS

Power consumption, Computer        174 K.W.
Space occupied, Computer         1,800 sq ft
Air conditioning                 Forced outside air.

MANUFACTURING RECORD

Number produced               1
Number in current operation   1

COST

Additional equipment       Magnetic storage
  $29,706.50
Rental rates for additional equipment:
  I.B.M.   card reader   $82.50 per month
  I.B.M.   card punch    $77.50 per month
Approximate cost of basic system   $750,000

PERSONNEL REQUIREMENTS

Daily operation       No. of Tech.
3 - 8 hour shifts          6
7 days/week

A minimum requirement of operation and servicing on a 24-hour-day, 7-day- week basis. No engineers are assigned to operation of the machine, but they are used for design, development of improvements and consultation when total breakdowns occur.

RELIABILITY AND OPERATING EXPERIENCE

Date unit passed acceptance test     1946
Average error free running period     5.6 hrs
Operating ratio    0.69   Good time   113 hrs
(Figures for 1955) Attempted to run   164 hrs/wk
No. of different kinds of plug-in units   44
No. of separate cabinets (excluding power and air cond.)   42
Operating ratio figures for 1954:
  Operating ratio   0.70   Good time   116 hrs
                    Attempted to run   166 hrs/wk

ADDITIONAL FEATURES AND REMARKS

There are four modes of operation: Continuous, Pulse time, Add time, or Instruction time.

A manual pre-set stop box is available.

Count instructions and transfer instructions are used.