Williams Tube memory, Selectron question, and Charactron

William Donzelli <aw288(a)osfn.org> wrote: I imagine you're thinking of Williams Tube memory, which was used on various computers before core memory was available, including the IBM 701 and 702 (their first mass-produced electronic computers for scientific and business applications, respectively). Williams tube memory worked by sensing the potential at the face of the tube, not by sensing the beam current. IBM apparently was never able to make Williams Tube memory work reliably at the density that they originally quoted to customers (1K bits per tube), so they scaled it back to 512 bits per tube with twice as many tubes. When core memory became practical, IBM retrofitted the 701s and 702s they had already sold. Meanwhile, Thomas Watson Jr. heard that the 705 team was planning to use Williams Tube memory instead of core because it was cheaper. He apparently said something about the stupidity of using something that doesn't work instead of something that does on the basis of the economy of the former. The 705 shipped with core memory. :-) As did allmost all IBM computers from then until the introduction of semiconductor main memory on the 360/85 and thin-film memory on the 360/95. Does anyone know how RCA's Selectron memory tube worked? I've seen pictures but no explanation. Memory wasn't the only part of early computers that used special and somewhat bizarre electron tubes. One of the earliest CRT display devices was the Charactron. This worked by defocusing the electron beam, using one set of deflection coils to steer the electrons through a character stencil (like a shadow mask), and a second set of deflection coils to steer the electrons to the desired character location on the screen. If memory serves, this type of display was used on Whirlwind. Presumably it was more economical than using a standard XY oscilliscope with either a hardware vector character generator or software. Eric