5 ms·

This is a demonstration board for the bigger brother, UE-1. UE-1 will be driven by paper tape, though core memory keeps being discussed. I don't think they ar

This is a demonstration board for the bigger brother, UE-1. UE-1 will be driven by paper tape, though core memory keeps being discussed. I don't think they are considering delay lines -- might be too challenging/fiddly.

codedokode 3y ago
By the way there are cheap and easy to use quartz delay lines used in old TVs.
- orbital-decay 3y ago
  Those provide 64 microseconds delays, which is probably too short to store data for a slow machine like this. Delay lines used in storage typically provided single-digit ms.
  - Animats 3y ago
    A few of those in series, with a regenerator stage after each one, would work. It's hard to find non-IC delay lines today. "Analog" delay lines in guitar pedals now use a charge-coupled bucket brigade IC. They're analog in amplitude, but discrete in time. I was expecting that someone would still be manufacturing some kind of acoustic delay line product, but there's not much out there. The EDSAC rebuild people built a delay line memory.[1] Not too complicated, but a pain to get it to work. You need a piezoelectric or magnetostrictive transducer driving a metal rod, with a receiving sensor at the other end. Liquid level sensors which work that way are common. A metal rod dips into the liquid, and a transducer at the top sends a ping down the rod. The impedance change where the rod enters the liquid causes a reflection, which is sensed by the transducer that sent the pulse. Converting one of those into a delay line might be possible. You need some length. The speed of sound in steel is around 5,000 meters per second, so you'll need 5 meters for a millisecond delay. This can be a coil; it doesn't have to be straight. A longer delay line can store more bits, but the cycle time is slower. These things are temperature sensitive, so they either have to be self-clocking or temperature controlled. [1] https://www.youtube.com/watch?v=9BA4AyvlKnM https://www.youtube.com/watch?v=9BA4AyvlKnM
    - orbital-decay 3y ago
      If I remember correctly some old textbooks I've read, these lines were usually made of invar or a similar alloy to avoid the thermal expansion, and the torsional wave spreads slower (around 3km/s). Reflections were dampened using rubber pads.
orbital-decay 3y ago
Torsion wire delay lines seem pretty DIY friendly, and resistant to interference. They've been used in low-end computers for a reason. (in contrast to the core memory)
- FullyFunctional 3y ago
  Delay lines are fascinating, but I don't see why this is easier than core memory; seems like you are trading an electronics problem for a mechanical one. Regardless, at the speeds they are targeting, I think delay lines might be difficult. Another interesting option (for ROM) is core rope memory. CuriousMarc has the ultimate explanation: https://www.youtube.com/watch?v=hckwxq8rnr0 https://www.youtube.com/watch?v=hckwxq8rnr0
  - Animats 3y ago
    Because, if you're using tubes, you don't want a huge number of them. Core memories need many drivers and sense amplifiers. Delay lines are inherently 1-bit devices.
  - orbital-decay 3y ago
    Core memory needs a lot of manual wiring, and you need two demultiplexers to address anything in it. Torsion wire delay line has no demultiplexer and is much simpler; it's basically a coil of invar wire on a spacer, with some rubber dampeners, an actuator, and a sensor. And it's inherently serial, many early calculators had serial architectures built around acoustic or IC delay lines. > at the speeds they are targeting, I think delay lines might be difficult Speed of the torsional wave is around 3000-3500m/s depending on the alloy you use. You can make the coil about several dozen meters long before running into issues (practical torsion wire delay lines were 20 to 80m long). That would give 6 to 27ms of delay, which can keep 600 to 2700 bits in the loop at 100kHz, or 10 times more at 1MHz. The same amount of cores would be far more labor intensive to make.

codedokode 3y ago

By the way there are cheap and easy to use quartz delay lines used in old TVs.

orbital-decay 3y ago
Those provide 64 microseconds delays, which is probably too short to store data for a slow machine like this. Delay lines used in storage typically provided single-digit ms.
- Animats 3y ago
  A few of those in series, with a regenerator stage after each one, would work. It's hard to find non-IC delay lines today. "Analog" delay lines in guitar pedals now use a charge-coupled bucket brigade IC. They're analog in amplitude, but discrete in time. I was expecting that someone would still be manufacturing some kind of acoustic delay line product, but there's not much out there. The EDSAC rebuild people built a delay line memory.[1] Not too complicated, but a pain to get it to work. You need a piezoelectric or magnetostrictive transducer driving a metal rod, with a receiving sensor at the other end. Liquid level sensors which work that way are common. A metal rod dips into the liquid, and a transducer at the top sends a ping down the rod. The impedance change where the rod enters the liquid causes a reflection, which is sensed by the transducer that sent the pulse. Converting one of those into a delay line might be possible. You need some length. The speed of sound in steel is around 5,000 meters per second, so you'll need 5 meters for a millisecond delay. This can be a coil; it doesn't have to be straight. A longer delay line can store more bits, but the cycle time is slower. These things are temperature sensitive, so they either have to be self-clocking or temperature controlled. [1] https://www.youtube.com/watch?v=9BA4AyvlKnM https://www.youtube.com/watch?v=9BA4AyvlKnM
  - orbital-decay 3y ago
    If I remember correctly some old textbooks I've read, these lines were usually made of invar or a similar alloy to avoid the thermal expansion, and the torsional wave spreads slower (around 3km/s). Reflections were dampened using rubber pads.

orbital-decay 3y ago

Torsion wire delay lines seem pretty DIY friendly, and resistant to interference. They've been used in low-end computers for a reason. (in contrast to the core memory)

FullyFunctional 3y ago
Delay lines are fascinating, but I don't see why this is easier than core memory; seems like you are trading an electronics problem for a mechanical one. Regardless, at the speeds they are targeting, I think delay lines might be difficult. Another interesting option (for ROM) is core rope memory. CuriousMarc has the ultimate explanation: https://www.youtube.com/watch?v=hckwxq8rnr0 https://www.youtube.com/watch?v=hckwxq8rnr0
- Animats 3y ago
  Because, if you're using tubes, you don't want a huge number of them. Core memories need many drivers and sense amplifiers. Delay lines are inherently 1-bit devices.
- orbital-decay 3y ago
  Core memory needs a lot of manual wiring, and you need two demultiplexers to address anything in it. Torsion wire delay line has no demultiplexer and is much simpler; it's basically a coil of invar wire on a spacer, with some rubber dampeners, an actuator, and a sensor. And it's inherently serial, many early calculators had serial architectures built around acoustic or IC delay lines. > at the speeds they are targeting, I think delay lines might be difficult Speed of the torsional wave is around 3000-3500m/s depending on the alloy you use. You can make the coil about several dozen meters long before running into issues (practical torsion wire delay lines were 20 to 80m long). That would give 6 to 27ms of delay, which can keep 600 to 2700 bits in the loop at 100kHz, or 10 times more at 1MHz. The same amount of cores would be far more labor intensive to make.