Zuse Z22
1958 · Valve Computer with Drum Store · Work 634 of 1,871
A valve computer of 1958 in a technical college room, a wall of cabinets in beige-grey sheet steel with open bays, in the bays horizontal rows of several hundred glass valves with a faint reddish glow, at the right a plugboard with round sockets and a bundle of thick orange cables, in front of the cabinets a desk in the same beige with an aluminium edge, a grey teleprinter at its centre, a sloping control panel at its right with rows of small keys in yellow, red, white and blue, paper tape curling from the teleprinter into a wire basket, a wooden swivel chair, daylight through net curtains.
- What it was used for
- The Z22 was Zuse KG's first stored-program computer and the first German tube computer built in series. The ZCOM Zuse Computer Museum names Bad Hersfeld as the place of manufacture, 1957 to 1961 as the build period and Lorenz Hanewinkel as its developer. The machine used about 400 tubes and 2,400 diodes; its store was a magnetic drum holding 8,192 words. The clock ran at about 140 kilohertz, an addition took 0.6 milliseconds and a multiplication 10 milliseconds. Fifty-six were built, priced between 150,000 and 230,000 marks. According to Professor Giloi, quoted by Horst Zuse, the Z22 brought data processing into German universities and scientific institutes; the first machine went to the TH Berlin in February 1958, the second to RWTH Aachen.
- What was new
- The stored program was not new, it was ten years old - but it was new for Zuse: for the first time programs could be held internally in a Zuse machine, which made it flexibly programmable. Programming was done in the Freiburger Code. The barb: the drum store this rested on was not Zuse's own. According to Horst Zuse's account, Zuse KG licensed the drum from Gerhard Dirks in 1957, at considerable cost. The computer, a great financial success for the company according to Horst Zuse - 56 units - thus stood on a bought-in licence.
What the sources leave open: The computing speeds differ: Horst Zuse gives 0.3 and 0.6 milliseconds for a fixed-point addition and 35 and 20 to 25 floating-point operations a second, the ZCOM 15 to 25 operations a second. The eight words of the Z22-1 belong to an additional core store beside the drum, not a contradiction. Both sources consulted give 56 as the number built.