Oldest operational computer was Re: cctalk Digest, Vol 54, Issue

I am sitting here, reading this thread, and am astounded by what people think tubes could do back in 1906. It would have been *impossible* to make any sort of computing device using the technology of the time. You would have better luck porting OS/2 to a 709. Tubes back then barely worked. When they did work, they barely amplified. And you were lucky to get 50 hours out of them. A try getting two that were vaguely similar electrically. And then try to find someone that actually knew how the things worked. Arguably, the best of the very early devices is the LRS Relay. They were very fragile devices, electrically and mechanically, and were something less than uniform in spec. In the US, the Audion was worse in every way. Even using three Audions in the same radio was so much of a handful that it was rarely tried. The only place tubes were used in signifcant numbers were some of the "high power" transmitters that basically used banks of tubes in parallel. In this configuration, there was some success, due to the inherent fault tolerant nature of the design. It was not until the Great War that tubes started to get reasonably uniform and "high" quality. The best example is probably the Western Electric VT-1, and that did not get good until 1917 or so. Even then, getting even a small number to work together was a chore. Signal Corps manuals of the time often include instructions telling how the radio operator should plow thru his allotment of twenty VT-1s to find three that would make the radio work properly. I have thought about how one would make a very early digital machine using tubes, and I have concluded that the very late 1920s is perhaps a good line to draw in the sand. The AC tubes were out in numbers and very consistent, high power rectifiers were also working well enough to eliminate the use of batteries, and even passive parts like resistors were finally coming out uniformly so every circuit did not have to be tweaked. Tubes and relays for motor control were well developed, and even phototubes were useful in a binary sort of way. The problem that always ends up being the show stopper is in RAM. Using a CRT for the memory was still off quite a few years, ferrite cores were not around for a few more, capacitors generally were too leaky to hold a charge long, magnetic recording was just not really there yet - so the only real option for online storage is an acoustic delay loop. Or paper, in the form of punch cards - which is exactly were the computer industry went. Cheap, easy, reliable, non-volatile. -- Will