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

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

valve.computer

Post reply on HN
Print view View original

71–80 of 87 posts

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

#71

Post by hilbert42 »

bregma wrote: post #64
hilbert42 wrote: post #42

Earlier quoted context omitted.

"They could've done 10 tubes in series at a reasonably safe 60 VDC, and they'd only need 20 amps." Thermionic vacuum tubes of this type usually have a specified maximum heater/cathode voltage rating which varies considerably according to design. Exceeding that rating and one risks a short between the heater and cathode. For these types of tubes heaters can safely operate up to 200V negative with respect to the cathod…

When I was in high school (many decades ago now) we had a vacuum tube tester with a switch that allowed you to select the heater voltage. We quickly discovered, devils that we were, that if you stuck a simple diode with a 1.5 V heater in the tester and cranked the voltage to max it would launch like a little rocket. Eye protection recommended.

"We quickly discovered, devils that we were, that if you stuck a simple diode with a 1.5 V heater in the tester and cranked the voltage to max it would launch like a little rocket."

Where I once worked we had several AVO Mk III valve testers† which we used in a nice little "demo" (for want of a better word) for both new employees and non-electronics types who'd occasionally wander into the engineering/electronics department.

We'd take a 7 or 9-pin miniature valve (preferability 9-pin) and place it under water and break the evacuating seal on its top, being evacuated the valve would instantly fill with water. Now with suitable settings on the AVO we'd get the water to boil with steam bubbling out of its top. This all happened whilst we nonchalantly went about our business pretending that nothing unusual was happening.

Sometimes the reaction from the newcomers/visitors was so funny that those of us who couldn't keep a straight face would quickly exit the lab and burst into hysterical laughter.

That was party trick number one, there were more: half fill a CRT with water by the same process and put it back into the monitor for some poor unsuspecting tech to discover. Another was our famous CO2-powered valve gun which we'd use to shoot 7-pin and 9-pin valves at high speed across the carpark aimed at the door of the electricians' department with whom we were continually at war. The valves would embed themselves in the wooden door up to the full length of their pins and rarely would the glass break. Electricians would come in next morning to find our little gifts awaiting them.

Yet another was the exploding electrolytic capacitor under one's seat. And there are many more to tell.

Believe it or not, we were quite a professional outfit and our work output was excellent. But it was the funniest and most enjoyable place I've ever worked at.

† https://www.radiomuseum.org/r/avo_valve_tester_mk3_mk_3.html

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

#72

Post by tlb »

kazinator wrote: post #63
cjs_ac wrote: post #57

Earlier quoted context omitted.

The difference is that for solid-state logic, the heat is purely a waste byproduct, whereas for thermionic valves, the heat is the energy used by the electrons to move between the electrodes, hence the name. If the valves are cold, you have to wait for them to warm up before they can do anything.

All the same, "cold boot" doesn't refer to letting tubes cool down. If power is restored while the tubes are still hot, it's still a "cold boot". The electrons are not moved by heat; they are moved by the electric potential between the electrodes. The heat goes into maintaining the cathode at a certain temperature , at which the electrons "boil off" in sufficient numbers, but that requires only a smidgeon of the ener…

Is this known to work? I would have thought that running a whole tube at high temperature would cause the grid to emit thermal electrons, creating a current between grid and plate. Even though the grid doesn't have the low-work-function coating that the cathode does, its surface area can be larger and it's usually more negative than the cathode so I'd expect substantial currents.

If this does work, you could save a lot of power by building heated, insulated enclosures for entire tube appliances rather than heating each cathode and cooling every tube.

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

#73

Post by kazinator »

Max-q wrote: post #67
kazinator wrote: post #63

Earlier quoted context omitted.

All the same, "cold boot" doesn't refer to letting tubes cool down. If power is restored while the tubes are still hot, it's still a "cold boot". The electrons are not moved by heat; they are moved by the electric potential between the electrodes. The heat goes into maintaining the cathode at a certain temperature , at which the electrons "boil off" in sufficient numbers, but that requires only a smidgeon of the ener…

The valves need to be warmed up can still be the source of the names "cold boot" and "warm boot", even if we today have given them different meaning.

The meanings we give them today go back almost 50 years.

Then the trail runs cold, pardon the pun.

According to Google n-gram searches, "cold reboot" and "warm reboot" didn't exist at all until the late 1970s.

Related terms like "cold boot" and "warm boot" come up, but only in references to footwear. Can't find any computer uses 1950-1970.

The "cold start" and "warm start" mostly come up in automotive, aviation or marine contexts, confounding the search. Likewise, not finding computer uses.

Not finding computer uses for "cold restart" and "warm restart", either.

All these terms take off as computer terms in the late 1970's.

By the way, an important feature of the warm reboot is (possibly) that data is still in memory (if you have the kind of machine whose memory is wiped when power is cut, not magnetic core). In machines with simple operating systems, you could recover your program or data from memory after a reset.

(I think the timeline in the n-grams coincides with the explosion in microcomputing and reflects that: penetration of the jargon into mainstream writing. Nevertheless, the case doesn't seem to be good though for a vacuum tube origin of warm {start/restart/reboot}.)

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

#74

Post by maccard »

naikrovek wrote: post #29
bentt wrote: post #24

"But most important of all, is to have a lovely wife, who knows you're daft as a brush, and that life together is brilliant." Hold out for the partner that cheers you on when you're doing what you love.

> Hold out for the partner that cheers you on when you're doing what you love. If only it were that easy. Those kinds of people are few and far between. I’m almost 50 and I don’t think I’ve ever even met a woman who has actively encouraged me about a single thing. I’ve been married twice and have 4 daughters.

If you've had 6 women close to you in your life and not one of them has supported you, the problem might be you and not them.

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

#75

Post by jhallenworld »

hilbert42 wrote: post #45
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?

"Could you lower the current requirement by thermally insulating the tubes?" The thermionic effect is very interesting, if the right material is used to coat the cathode then very large emissions can be had. Combinations of oxides such as barium, strontium and others can have both low work functions and high emissions. Currents in the region of over 100A/sq cm can be achieved. Thus, valves/tubes could be designed to…

The directly-heated cathode (meaning that the heater is the cathode) tubes have another advantage: they are nearly instant turn-on, no warm-up needed. Same as vacuum fluorescent displays.

Reminds me: there are new tubes based on VFD:

https://www.korgnutube.com/en (only 12mW heater power)

Very old 1920s tubes also used direct cathodes (but used a huge amount of heater power). If you look at the circuits, they had to jump through hoops to have the desired grid to cathode bias while at the same time providing the heater current. I think this would be easier for logic gates: set all of them to ground.

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

#76

Post by klyrs »

kazinator wrote: post #56
01HNNWZ0MV43FF wrote: post #52

Earlier quoted context omitted.

Silicon. Silicone is the plastic used to make crummy kitchen utensils

I'm amazed I made the typo twice in the same post. Kazinator comments containing "silicone": https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu... Kazinator comments using "silicon" https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...

> kazinator|7 years ago ... Love the irony of how silicon is used.

Common confusion; silicon is a metalloid, irony is metallic

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

#77

Post by ssdsa »

It's really cool to design all those NOR gates using thermionic valves, as shown in the schematics in the middle of the article. I just wonder if using two regular diodes in the input paths of each NOR gate and another diode in the output path is a little bit of "cheating", since diodes are somewhat newer technology than thermionic valves.

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

#78

Post by tlb »

tlb wrote: post #72
kazinator wrote: post #63

Earlier quoted context omitted.

All the same, "cold boot" doesn't refer to letting tubes cool down. If power is restored while the tubes are still hot, it's still a "cold boot". The electrons are not moved by heat; they are moved by the electric potential between the electrodes. The heat goes into maintaining the cathode at a certain temperature , at which the electrons "boil off" in sufficient numbers, but that requires only a smidgeon of the ener…

Is this known to work? I would have thought that running a whole tube at high temperature would cause the grid to emit thermal electrons, creating a current between grid and plate. Even though the grid doesn't have the low-work-function coating that the cathode does, its surface area can be larger and it's usually more negative than the cathode so I'd expect substantial currents. If this does work, you could save a l…

Though I guess you could save even more power by using transistors.

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

#79

Post by kazinator »

ekidd wrote: post #66
kazinator wrote: post #61

Earlier quoted context omitted.

Filaments experience a high inrush current on startup because their resistance is lower when they are cold. That's why incandescent bulbs often burn out on powerup, rather than in the middle of a duty cycle. Tube filaments last a good long time though, particularly in small signal tubes. They do not shine like light bulb filaments; they glow red. The circuit designer also has a say in it; tube filaments can be operat…

> Once everyone has 50 year bulbs, you're out of business. This seems to have been the issue with the expensive Philips Hue LED bulbs (the ZigBee ones). We installed ours close to a decade ago, and we took them with us when we moved to a new house. I don't think I've replaced a single one yet. Philips seems to have de-emphasized that set of bulbs in favor of cheaper models, as far as I can tell?

I have 13-y-o Phillips LED flood lights in some track lighting (50W equivalents, maybe?). Working great!

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

#80

Post by hilbert42 »

jhallenworld wrote: post #75
hilbert42 wrote: post #45

Earlier quoted context omitted.

"Could you lower the current requirement by thermally insulating the tubes?" The thermionic effect is very interesting, if the right material is used to coat the cathode then very large emissions can be had. Combinations of oxides such as barium, strontium and others can have both low work functions and high emissions. Currents in the region of over 100A/sq cm can be achieved. Thus, valves/tubes could be designed to…

The directly-heated cathode (meaning that the heater is the cathode) tubes have another advantage: they are nearly instant turn-on, no warm-up needed. Same as vacuum fluorescent displays. Reminds me: there are new tubes based on VFD: https://www.korgnutube.com/en (only 12mW heater power) Very old 1920s tubes also used direct cathodes (but used a huge amount of heater power). If you look at the circuits, they had to j…

"Very old 1920s tubes also used direct cathodes (but used a huge amount of heater power)."

Yeah, and not-so-old ones too (that is, ones designed in the 1940s). I've a couple of 100TH power triodes whose directly heated thoriated tungsten cathodes consume just over 30 Watts (5V @ 6.3A) yet their plate dissipation is only around 100W. That's pretty miserable efficiency. (They look very pretty when working though.)

You're right about jumping through hoops, circuis become messy and contorted. Also, there's the messy business of eliminating AC filament hum, thus the commonplace practice of using a humdinger circuit on directly-heated triodes such as the 2A3.

Nearly instant turn on can also be a disadvantage when they're used as rectifiers. Tubes like 80, 5Y3G, 5R4G, etc. supply HT long before loading occurs from the indirectly heated ones. In unregulated or poorly designed power supplies it can put additional strain on the PS's electrolytic capacitors.

I've often wondered why rectifiers, especially low power one like those mentioned, remained so popular for so long—or why it took so long for indirectly-heated, unipotential cathode tubes such as the 6X4 to become popular. Cost and ease of manufacturing I suppose.

Post reply on HN