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I have this nagging desire to build a completely useless piece of archaic technology using modern tools. A memory delay line. I would love to use fiber optics but and electrical wire works too. Obviously it would have to be really long to fit any significant number of bits in it, and even then it would be on the order of hundreds or thousands of bits. But the idea of storing memory as signals moving near the speed of light just tickles me pink.
@freemo A slower version could be an acoustic delay line.
@hendrikboom3 yea but those are pretty common and can be bought ready made. Plus it seems to lack the cool factor in my mind.
@freemo The Bendix G-15d computer used delay lines on a magnetic drum. The spacing between read and write heads determined the delay.
Those delay lines contained the main memory *and* the registers (such as the arithmetic accumulator).
@hendrikboom3 I suspect you mean magnetostrictive delay lines. They were the next generation right after mercury delay lines. They operated via torsional waves in a wire. very cool stuff.
@hendrikboom3 A magnetic drum isnt a delay line though, so I'm confused what you mean then.
@freemo I wasn't aruond for the mercury delay lines. They were from the 40's and 50's, right? And you can still get them nowadays? I didn't get into computing until '62. I remember reading about William's tube memories. Why do I get the idea they were grasping at straws back then to get anything, just anything, to work?
@hendrikboom3 mercury delay lines were at the birth of computing. ENIAC had one as its memory. I highly doubt you can get them today. They are insanely expensive, bulky, poisonous, and hold very little memory. I cant imagine any use for them still being made today.
@freemo No, I did mean a real magnetic drum on this machine, acquired by the university in 1957. I got to use it in1962. I spent a happy summer hanging about the university's air-conditioned computer room reading its circuit diagrams to learn how it operated. It was a truly magnificent kludge.
Main memory consisred of a number of these recirculating tracks, each was 108 words of 29 bits each -- 7 hex digits and a sign bit. The instructions had a source memory line, a destination memory line, and specifications when the instruction was to be executed and when the next one was to be read. These times were essential -- they determined which words were being read and rewritten and thus possibly modified as the drum turned.