All about the Bendix D-12

The Bendix D-12

The Bendix D-12 was not a General Purpose Computer. It was a Digital Differential Analyser.

The following description of the Bendix D-12 appeared in "A Second Survey of Domestic Electronic Digital Computing Systems" by Martin H. Weik, dated 1957. (I hope the name of the report is correct. The author and date are).

APPLICATIONS

Manufacturer: Solution of differential equations

Government Sample: Griffiss Air Force Base: General scientific

NUMERICAL SYSTEM

Internal number system		Binary coded decimal
Decimal digits per word  	8
Arithmetic system  		Fixed point 
Number range  			-5.0000000 to +4.9999999

As this system is a digital differential analyzer, usual digital computer instructions are not used. The computer employs a semi-fixed program.

ARITHMETIC UNIT

Add Time (excluding storage access) 43 Microsec
Construction                        Vacuum tubes 
Basic pulse repetition rate         200 Kc/sec 
Arithmetic mode         Serial 
Timing                  Synchronous 
Operation               Sequential

Decimal digits are treated serially, whereas their binary codes are held in parallel.

STORAGE

     Media        Words      Binary Digits 
Magnetic Drum      650          22,000

Access times are not relevant because of the fixed program.

Government Sample: Griffiss Air Force Base: This system has 60 integrators.

INPUT

  Media              Speed
Paper Tape         6 dig/sec

OUTPUT

  Media              Speed 
Typewriter        10 dig/sec 
Graph Plotter     20 dig/sec, 100 steps/inch

Government Sample: Griffiss Air Force Base: This system has a teletype punch and a visual CRT display.

CIRCUIT ELEMENTS ENTIRE SYSTEM

Tubes                     700
Tube types                  6 
Crystal diodes          2,200 
Separate cabinets           2

CHECKING FEATURES

Fixed Overflow in addition
Prescribed code as a result of addition

POWER, SPACE AND WEIGHT

Power, computer         7.5 KW 
Power, air cond.        105 cu.ft.  25 sq.ft.
Weight, computer        2,000 lbs.

A desk is provided in addition to the computer console proper.

PRODUCTION RECORD

The Bendix D-12 is no longer in production and is manufactured only when a customer's needs can be by no other equipment. The DA-1 used with the C-15D General purpose Computer System is based on the D-12 and uses the memory of the G-15D for combined GPC and DDA operation. The DA-1, while lowpriced, is therefore equipped with 108 integrators.

Apologies for the poor quality of the picture below, which is a copy of a copy of copy ... Still, it gives a rough idea of the appearance of the D-12.

My thanks to Eric Barbour for providing this information.