Re: [TUHS] core

Tim Bradshaw <tfb(a)tfeb.org> commented on a paper by Tommy Flowers on the design of the Colossus: here is the reference: Thomas H. Flowers, The Design of Colossus, Annals of the History of Computing 5(3) 239--253 July/August 1983 https://doi.org/10.1109/MAHC.1983.10079 Notice that it appeared in the Annnals..., not the successor journal IEEE Annals.... There is a one-column obituary of Tommy Flowers at http://doi.ieeecomputersociety.org/10.1109/MC.1998.10137 Last night, I finished reading this recent book: Thomas Haigh and Mark (Peter Mark) Priestley and Crispin Rope ENIAC in action: making and remaking the modern computer MIT Press 2016 ISBN 0-262-03398-4 https://doi.org/10.7551/mitpress/9780262033985.001.0001 It has extensive commentary about the ENIAC at the Moore School of Engineering at the University of Pennsylvania in Philadelphia, PA. Its construction began in 1943, with a major instruction set redesign in 1948, and was shutdown permanently on 2 October 1955 at 23:45. The book notes that poor reliability of vacuum tubes and thousands of soldered connections was a huge problem, and in the early years, only about 1 hour out of 24 was devoted to useful runs; the rest of the time was used for debuggin, problem setup (which required wiring plugboards), testing, and troubleshooting. Even so, runs generally had to be repeated to verify that the same answers could be obtained: often, they differed. The book also reports that reliability was helped by never turning off power: tubes were more susceptible to failure when power was restored. The book reports that reliability of the ENIAC improved significantly when on 28 April 1948, Nick Metropolis (co-inventor of the famous Monte Carlo method) had the clock rate reduced from 100kHz to 60kHz. It was only several years later that, with vacuum tube manufacturing improvements, the clock rate was eventually moved back to 100Khz. ------------------------------------------------------------------------------- - Nelson H. F. Beebe Tel: +1 801 581 5254 - - University of Utah FAX: +1 801 581 4148 - - Department of Mathematics, 110 LCB Internet e-mail: beebe(a)math.utah.edu - - 155 S 1400 E RM 233 beebe(a)acm.org beebe(a)computer.org - - Salt Lake City, UT 84112-0090, USA URL: http://www.math.utah.edu/~beebe/ - -------------------------------------------------------------------------------