
Acoustic delay line memory (2014) - sndean
https://jhallenworld.blogspot.com/2014/01/acoustic-delay-line-memory.html
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kdoherty
There is also a fantastic video where Cliff Stoll describes the Friden EC-132
calculator and shows off its acoustic delay line here:
[https://youtu.be/2BIx2x-Q2fE](https://youtu.be/2BIx2x-Q2fE)

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dwarman
There is another kind of acoustic delay line that was used in late 50's -
early 60's that used nickel strips and took advantage of magnetostrictive
property of Ni. I'm calling it acoustic because the memory was in the form of
a compression wave propagated from driving magnet to sensing coil, then
regenerated. Elliott Brother's 803 series computers used these for the CPU
registers.

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Zenst
I thought the UNIVAC used a form of wire memory,
[https://en.wikipedia.org/wiki/Plated_wire_memory](https://en.wikipedia.org/wiki/Plated_wire_memory)
So calling it acoustic memory does seem a stretch for me, but then any
electrical pulse plugged into a speaker would have an acoustic sound.

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todd8
Mercury delay lines were a form of memory that predates and is distinct from
plated wire memory. Plated wire memory is magnet memory, like core memory, but
with permalloy coated wires rather than little permalloy donuts like the
elements of core memory.

Delay line memory uses a transducer that puts vibrations into a medium in a
tube (mercury) that travel the length of the tube at the speed of sound
through that medium (1450 m/s) a transducer at the other end picks up the
vibrations and decodes them back into bits. While the signals are being sent
down the tube they are "in memory". By sending the signals back to the
beginning of the tube a set of bits can be kept recycling indefinitely (120
bits per delay line in the UNIVAC I).

The UNIVAC I only had 1000 thirty-five bit words in its memory. These were
store in a set of these mercury delay lines.

In my first digital design lab course at MIT there were a few old delay line
memories kicking around which I briefly considered using for a project. I
ended up needing only 5 shift registers of around 6 bits each so I just used
flip flops to build them for the nim-playing computer I built.

