The IBM 609 Calculator

The IBM 609 Calculator. Announced 26 April 1960 and withdrawn 1 July 1968. This is a faster version of the solid-state 608, and the last of IBM's line of punched-card calculators. Like previous models, it performed addition, subtraction, multiplication, and division on data read from its card reader, punching the results on the input cards themselves, or on subsequent cards, according to instructions from its plugboard program, supporting up to 144 program steps including conditional branching. It featured up to 384 12-decimal-digit words of core storage, direct-add storage words, 200-card-per-minute speed, and no special power or cooling requirements. Weight: 1400 pounds. Volume: 50 cubic feet. Dimensions: 50" × 29" × 60". Cost: $36,000 to $55,000; Rental: $735 to $1100 per month, according to model and options (mainly memory and program steps).

IBM 609 in use — *Photo:* US Army Ballistics Research Lab Report No. 1115, March 1961.

An IBM 609 spec sheet compared the 609 with the 604 for various applications, such as construction earthwork computations:

	604	609
Calculations of miles of highway per hour:	3/5	24
Number of Card Passes Required:	28	1
Number of Control Panels Required:	28	2

The 609 was designed entirely by one person, L. Roy Harper, who had it on the market within 14 months of its conception. Its purpose was to retire the huge installed base of the 12-year-old 604. It was apparently rather popular in Europe.

Aside from increased speed, program steps, and memory capacity over the earlier 60x models, the 609 featured built-in error checking: "All input, calculated, and output information is tested for error conditions. Every data transfer and arithmetic operation is parity checked. The 609 Calculator uses a unique type of matrix-analysis adder which includes the the 'checking bit' in its arithmetic operation. Consequently, it should not be necessary, as in previous 600 series unit record calculators, to recalculate results for checking, although the 609 retains this recalculating ability. Thus, the time formerly devoted to recalculating in a program can now be used to increase the amount of calculation performed on a card in one pass through the machine. By means of control panel wiring, detected errors can be selected into separate pockets, or the machine can be stopped."

Sources: Assorted IBM circulars, pamphlets, and news releases, 1960, from the IBM Archive.

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IBM Calculators
IBM 601 602 603 604 605 607 608 610