IBM 709

IBM 709
Manufacturer:	International Business Machines
Year Announced:	January, 1957
Year Discontinued:	April, 1960
Form Factor:	mainframe
Word Size:	36 bits
Logic Type:	vacuum tubes
Clock Speed:	24 μsec (basic add instruction)
Memory Speed:	12 μsec
Operating System:	SOS, IBSYS, IBJOB
Predecessor(s):	IBM 704
Successor(s):	IBM 7090
Price:	US$2.6M (and up)

The IBM 709 was IBM's last major vacuum tube scientific mainframe (built at a time when computers for scientific and business computing used separate instruction sets). It was announced in January, 1957

Major advances over its predecessor, the IBM 704, included indirect addressing, and channels (called 'Data Synchronizers' at the time). A Data Synchronizer had two channels, to each of which could be attached a card reader, card punch and printer; up to eight magnetic tape drives could be attached to a single channel.

One peculiarity of the index registers was that there were three, selected by a 3-bit field in the instruction, each register being selected by one bit; if more than one bit was set, the registers indicated were logically ORed together before being used!

One major advance pioneered on the 709 was time-sharing; the first time-sharing operating system, CTSS, was first experimentally operated on a 709.

Its lifetime was shortened by the switch to transistors as the technology for computers.

Further reading

• Charles J. Bashe, Lyle R. Johnson, John H. Palmer, Emerson W. Pugh, IBM's Early Computers, MIT Press, Cambridge, 1986

External links

• 709 Data Processing System - IBM Archive page
• From the IBM 704 to the IBM 7094
• The IBM 704 and 709 Systems