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).
Manufacturer: Solution of differential equations
Government Sample: Griffiss Air Force Base: General scientific
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.
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.
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.
Media Speed Paper Tape 6 dig/sec
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.
Tubes 700 Tube types 6 Crystal diodes 2,200 Separate cabinets 2
Fixed Overflow in addition
Prescribed code as a result of addition
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.
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.
