Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

A Vacuum Tube Single Board 1-Bit Computer [video]

youtube.com

Post reply on HN
Print view View original

31–40 of 42 posts

Re: A Vacuum Tube Single Board 1-Bit Computer [video]

#31

Post by orbital-decay »

FullyFunctional wrote: post #24
orbital-decay wrote: post #9

Earlier quoted context omitted.

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)

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

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.

Re: A Vacuum Tube Single Board 1-Bit Computer [video]

#32

Post by kazinator »

Tangurena2 wrote: post #22
deelowe wrote: post #15

Earlier quoted context omitted.

We could just as easily ask why would you use tubes for guitar distortion?

Hollow state devices saturate differently than solid state devices. Although FETs have similar saturation curves as tubes/valves (sometimes called "glass FETs" - both are voltage amplifiers while transistors are current amplifiers). The fuzz in most guitar amps is the hard saturation that transistors do. So I guess using tubes/valves for guitar distortion is a fashion/trend. There are a number of pre-amps for electri…

> The fuzz in most guitar amps is the hard saturation that transistors do.

Most guitar amps in what sense? Most guitar amp units shipped? Probably the biggest volume there is amateurs.

> recreate some sounds from the 40s-60s.

Try 40s-90s-00s--...?

Tubes are commonly used right for tones right up to the heaviest metal. It's common for some solid state driving device to be used, like an overdrive pedal. That doesn't necessarily provide any needed gain, but rather shapes the clean tone, which has an effect on what kind of distortion you get.

(Ironically, one difference between "old school" metal and "modern" metal that amps used in modern metal have more tubes: like three 12AX7's in the preamp rather than two. Nothing needs another vacuum tube more than "modern"!)

In other words, the use of tubes in rock guitar continued to evolve well into the 1990s. So tubes are the key to authentically reproducing the sounds heard in 90s and later metal, not just 40s through 60s.

Which is not to deny that solid state devices aren't used for distortion, either as driving elements for tubes or alone.

Re: A Vacuum Tube Single Board 1-Bit Computer [video]

#33

Post by jovial_cavalier »

kazinator wrote: post #28
jovial_cavalier wrote: post #16

Earlier quoted context omitted.

Idk. Why not just simulate it on your Ryzen 9?

- Because it's not a hardware project at all then. Using transistors versus tubes is still a hardware project on the same level of abstraction. - You've not gotten away from hardware; it's still there. - You're using billions of transistors to simulate the operation of dozens of transistors/tubes, which is inelegant. The chip with those transistors may be small, much smaller than your project, but, in theory, your de…

The guy knows that tubes are not the most efficient way to implement this. He's making it with tubes because it's cool. It's not that hard to understand.

Re: A Vacuum Tube Single Board 1-Bit Computer [video]

#34

Post by Animats »

orbital-decay wrote: post #10
codedokode wrote: post #8

Earlier quoted context omitted.

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

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.

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

Re: A Vacuum Tube Single Board 1-Bit Computer [video]

#35

Post by orbital-decay »

Animats wrote: post #34
orbital-decay wrote: post #10

Earlier quoted context omitted.

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.

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…

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.

Re: A Vacuum Tube Single Board 1-Bit Computer [video]

#36

Post by kazinator »

jovial_cavalier wrote: post #33
kazinator wrote: post #28

Earlier quoted context omitted.

- Because it's not a hardware project at all then. Using transistors versus tubes is still a hardware project on the same level of abstraction. - You've not gotten away from hardware; it's still there. - You're using billions of transistors to simulate the operation of dozens of transistors/tubes, which is inelegant. The chip with those transistors may be small, much smaller than your project, but, in theory, your de…

The guy knows that tubes are not the most efficient way to implement this. He's making it with tubes because it's cool. It's not that hard to understand.

The topic has changed in this subthread; this is now why build something (with discrete components, be they transistors or tubes) rather than simulate.

The educational value of building hardware is obvious to me; it cannot be replaced with simulation, and simulation runs on hardware that someone built, who knew how.

Re: A Vacuum Tube Single Board 1-Bit Computer [video]

#37

Post by jovial_cavalier »

kazinator wrote: post #36
jovial_cavalier wrote: post #33

Earlier quoted context omitted.

The guy knows that tubes are not the most efficient way to implement this. He's making it with tubes because it's cool. It's not that hard to understand.

The topic has changed in this subthread; this is now why build something (with discrete components, be they transistors or tubes) rather than simulate. The educational value of building hardware is obvious to me; it cannot be replaced with simulation, and simulation runs on hardware that someone built, who knew how.

Good to know that the topic has changed. Let me know if it changes again!

Re: A Vacuum Tube Single Board 1-Bit Computer [video]

#39

Post by calamari4065 »

kazinator wrote: post #6

Why would you use tubes if you're not making guitar distortion? Do you really need pentodes at the speeds involved? It looks like the guy is toggling a switch by hand to generate a clock signal. Pentodes are devices for RF amplification. Those 6AU6 tubes are 7 pin units, but they contain only one pentode element. Two pins for the heater, then five pins to hook up the pentode. There exist common 8 or 9 pin tubes that…

He's building a CPU from scratch. Practicality is not a concern at all.

Re: A Vacuum Tube Single Board 1-Bit Computer [video]

#40

Post by j_not_j »

asddubs wrote: post #11
kazinator wrote: post #6

Why would you use tubes if you're not making guitar distortion? Do you really need pentodes at the speeds involved? It looks like the guy is toggling a switch by hand to generate a clock signal. Pentodes are devices for RF amplification. Those 6AU6 tubes are 7 pin units, but they contain only one pentode element. Two pins for the heater, then five pins to hook up the pentode. There exist common 8 or 9 pin tubes that…

Why not tubes? Anyone building a computer this primitive out of discrete components isn't doing it because of its utility anyway

Tubes. And diodes (see the BOM).
Post reply on HN