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A modern 8 bit design, built using 1950s thermionic valves

valve.computer

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Re: A modern 8 bit design, built using 1950s thermionic valves

#12

Post by dang »

dr_dshiv wrote: post #11
dang wrote: post #6

[stub for offtopicness]

Is that a joke? Because this is the most hackernews article ever

Oh the article is thoroughly on topic! I mean the comments related to Valve the company. The thread was filling up with those before we changed the title. (Submitted title was "Valve.computer".)

Sometimes when there are too many offtopic comments like this I make a stub comment, move all the offtopic subthreads underneath it, and then collapse it.

https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...

Re: A modern 8 bit design, built using 1950s thermionic valves

#17

Post by doe_eyes »

cellularmitosis wrote: post #16

> 200 amps Something I’ve been curious about: is the current actually required for the thermionic effect, or just the heat? Could you lower the current requirement by thermally insulating the tubes?

They are insulated really well - by vacuum!

I'm actually surprised by the figure, though. A small tube requires about 300 mA at 6 V, and the trick is that you can connect the heaters in series instead of doing it all in parallel and pumping out a ton of amps at a very low voltage.

They could've done 10 tubes in series at a reasonably safe 60 VDC, and they'd only need 20 amps.

Back in that era, because both valves and relays were expensive, it was also common to use them more creatively than just constructing standard logic gates. You'd try to make a full adder or a flip-flop cell as an analog circuit, breaking the abstractions we're now used to - but also saving components.

Re: A modern 8 bit design, built using 1950s thermionic valves

#18

Post by Ductapemaster »

cellularmitosis wrote: post #16

> 200 amps Something I’ve been curious about: is the current actually required for the thermionic effect, or just the heat? Could you lower the current requirement by thermally insulating the tubes?

Current into a low-resistance "heater" element is used to produce the heat required for Thermionic Emission [0] in a vacuum tube. You only need the heater/emitter to be hot, and insulating the tubes would just spread the heat around to everything inside of it — at some extreme, making everything into an emitter, instead of elements that control the emission.

[0] https://en.wikipedia.org/wiki/Thermionic_emission

Re: A modern 8 bit design, built using 1950s thermionic valves

#19

Post by mrob »

cellularmitosis wrote: post #16

> 200 amps Something I’ve been curious about: is the current actually required for the thermionic effect, or just the heat? Could you lower the current requirement by thermally insulating the tubes?

Perhaps the inside of the tube could be coated with a thin layer of gold using evaporative deposition before the grid/plate/filament/etc is added, like on spacesuit visors for IR reflection.
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