5 ms·
Admiral Grace Hopper Explains the Nanosecond: https://youtu.be/9eyFDBPk4Yw https://youtu.be/9eyFDBPk4Yw
by maxmcd 3y ago
Admiral Grace Hopper Explains the Nanosecond: https://youtu.be/9eyFDBPk4Yw https://youtu.be/9eyFDBPk4Yw
- dylan604 3y agoThe first time I saw one of her demonstrations of a nanosecond, I was confused when she pulled out a length of wire. I don’t remember what class it was in or what context the video was being used, but this was 6th grade
- Mountain_Skies 3y agoPossibly an urban legend but there's a story about a company in India that ordered a Soviet made computer system that has an sloppy spool of wire attached to the main board. They contacted the Soviet institute that built the computer system and it was explained that the computer needed a timing delay between two components but didn't have the proper ICs on hand so they used a precise length of wire to introduce the needed delay to make the timing correct.
- defrost 3y agoAs a stone cold fact physical mediums with known delay timings were once used as memory storage for computers and as "echo removal" filters in radar installations. Although a mathematician, Turing took quite an interest in the engineering side of computer design. There was some discussion in 1947 as to whether a cheaper substance than mercury could not be found for use as an ultrasonic delay medium. Turing's contribution to this discussion was to advocate the use of gin, which he said contained alcohol and water in just the right proportions to give a zero temperature coefficient of propagation velocity at room temperature. ~ MAURICE V. WILKES 1967 A CM Turing Lecture https://sci-hub.ru/10.1145/321439.321440 https://sci-hub.ru/10.1145/321439.321440 https://en.wikipedia.org/wiki/Delay-line_memory https://en.wikipedia.org/wiki/Delay-line_memory https://www.theregister.com/2013/06/28/wilkes_centenary_mercury_memory/ https://www.theregister.com/2013/06/28/wilkes_centenary_merc...
- foobarian 3y agoThey are still used to test networking equipment under long propagation delays. Spools of fiber hundreds of miles long.
- dylan604 3y agoBack in the old days of analog video, component video was three separate cables. When we made custom cables, we had to ensure the cables were the same length to ensure the timing was within tolerance. The day we got to switch to digital SDI which also included audio as like a gift from the gods
- crote 3y agoThis is still a problem for modern multi-lane digital connections, like PCI Express. The solution? Make each individual lane self-timing, and compensate for it digitally in the receiver buffer.
- franky47 3y agoThis was probably also due to impedance matching between all the lines involved. Digital signals (when using N/P balanced lines) also have this problem, to a lesser extent. Some CAD EE design software have ways to design squiggly traces to balanced impedances in traces that have to go around corners on the PCB and end up with different lengths.
- db48x 3y agoThere were a lot of delay–line memories back in the day. It wasn’t just that they didn’t have memory chips; memory chips hadn’t been invented yet. https://www.youtube.com/watch?v=2BIx2x-Q2fE https://www.youtube.com/watch?v=2BIx2x-Q2fE
- mikhailfranco 3y agoThis is the method used to add delays for HFT to ensure fair(er) markets for all participants on the IEX exchange. Flash Boys, Michael Lewis https://en.m.wikipedia.org/wiki/Flash_Boys https://en.m.wikipedia.org/wiki/Flash_Boys