It wasn't until working with valve hardware that I finally grokked the original difference between a cold boot and a warm one.

It was amazing to see the battery array discharge ammeter at 5000 amps when utility power went out.

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 energy. Though depending on it, tubes are incredibly wasteful of heat.

So you say silicon and other parts don't require heat? Check that data sheet again! If the part's operating range is from -40°C to 70°C, then that part requires heat. If the ambient temperature happens to be -100°C, you have to heat it, perhaps by installing a heating filament into the chassis.

E.g. check the TI datasheet for the NE5532 op-amps:

Free air operating temperature:

NE5532, NE5532A: 0 to 70°C.

SA5532, SA5532A: –40 to 85°C.

(That standard part is quite delicate there, only down to zero!)

Conversely, thermionic tubes for a hot environment could be built without heating filaments. If the ambient temperature is 500°C, and that happens to be quite enough for that tube's cathode, then it Just Works, like your NE5532 IC at 3°C.

There's a lot of physics and engineering behind thermionic emission in a typical vacuum tube and the subject shouldn't be overlooked just because tubes are less commonplace than they once were.

Until the transistor became popular in the latter half of the 20th C. essentially all of electronics relied upon thermionic emission so much effort went into understanding it. Moreover, it's still very important in specialized areas such as in scientific instruments, high power transmitting tubes, TWTs (Traveling Wave Tubes), CRTs, etc.

Thermionic emission obeys Richardson's Law—after physicist Owen Richardson who received the Nobel Prize for his work in 1928, and its study is an essential part of thermodynamics: https://en.m.wikipedia.org/wiki/Thermionic_emission.

When I was learning about this stuff I had a little book titled Thermionic vacuum tubes and their applications by Sir Edward Appleton (who is more famous for his wartime research into radar). Still, for anyone who's interested in thermionic emission then this could be a useful reference.

I'd add that when it comes to practical methods of manufacturing thermionic cathodes, info on low work function oxide emitters etc. then there are references that are better or more practically orientated (but offhand I cannot remember the names of any).

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.

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}.)

One difference is that the valves have more chance of burning out on a cold boot due to the temperature change.

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 operated over a range of currents: you can run tubes hotter or colder. In a digital application, you'd probably want to go as cold as you can get away with for longer life.

Tubes have various modes of failure in addition to burned out filaments, like "gassing out", or the cathode emission decreasing, eroding the gain. Of course, abnormal conditions like parts melting from overcurrent.

Speaking of incandescent bulbs: those are victims of planned obsolescence. A bulb can easily be made that will last 50 years; it's just not profitable because you can't charge 50 times more for it than one that burns out in a year. 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?

Warm boots can save time by not repeating all the boostrapping steps. In a warm boot, you typically don't execute any power-on self-checks, for starters.

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.

I met my second wife this way, and our 6 years together were the best of my life. She was killed by a Russian tank in Ukraine in January, and I miss her more than anything.

One piece of advice I do have, though: hold out for someone who's a great partner who you really enjoy spending time with. Don't settle for someone who obviously isn't just because other people are pressuring you to "find someone".

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?

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.

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 cathode and about 100V positive.

In my post I suggested substituting a tube that's more common in the West—the 12AT7, it has the advantage of having a 'tapped' heater which means it can be wired in parallel mode to operate at 6.3V or in series mode at 12.6V. At 12.6V the current would be halved: https://en.wikipedia.org/wiki/12AT7 (pins 4 and 5, the tap on pin 9).

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

As the tubes are at high vacuum, they are already well-insulated, so I imagine that most of the heat loss is via infra-red radiation. I have a very vague recollection that, in thermionic tubes, the anode has to be kept reasonably cool so that it is not emitting electrons itself. I would be surprised if there are any low-hanging fruit to be plucked here, especially given that vacuum tubes were important technology for a half-century.

[1] https://en.wikipedia.org/wiki/6N3P

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 be much smaller and have much smaller currents. For a digital application such as this only a very small cathode current would be needed, this then would mean a much smaller heater could be used.

In the past, miniaturizing vacuum tubes was desirable but wasn't a major priority and further development was stopped when the transistor became available.

That said, in the 1950s portable tube radios were available that used much less heater power than their mains-operated counterparts, for example tubes like the 3V4. It has a directly-heated cathode and a filament/ heater voltage of 1.4V and current of only 100mA (in series mode it operates at 2.8V at only 50mA).

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.

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.

As others have mentioned, the 200amps of this case could be reduced substantially by running filaments in series (can be done with 6.3v heaters as the error from a common 5v or 9v supply is more than if you pair them up and use a 12V supply) though this introduces the failure mode of old Christmas tree lights.

Source: I make vacuum tubes.

https://vinylsavor.blogspot.com/2021/11/tube-of-month-6bh11....

This one has two diodes and two triodes.

https://vinylsavor.blogspot.com/search/label/6AY11

And in this very design, they chose "6N3P valve contains 2 triodes around a single heater, halving the physical size and power requirements."

There may have been tubes made where the triode function can be pretty rough (sufficient for a digital circuit) and several of them could share one enclosure. In the tubes shown above, apparently the limit was the number of pins on the socket - but also that all these active elements do not share any pin.

Insulating the whole thing would run into issues like burning wire insulation.

In some of this stuff, over half of the power supplies output was dumped as heat in resistive divider networks just to bias things correctly and ensure operation. The filaments worked out to less than a fifth of the load in many cases.

Coming from a background of transistors and chips, it was wild to see so many 5 watt or more resistors in use.

I've not used 6N3P tubes before but looking at the circuit it seems to me a 12AT7 (an old favorite of mine) would substitute in that circuit almost without alteration. Then again with a tweak or two either the higher gain 12AX7 or its lower gain cousin the 12AU7 would do.

This guy actually did it. What a fun project it must have been. Super interesting read.

One detail in the introduction that made me a bit puzzled: "The Valve.Computer is an 8 bit computer, with the usual 12 bit address and data buses". In an 8 bit CPU, we had "the usual 16 bit address bus and the 8 bit address bus".

Thank you for making it happen and sharing it here

Super interesting read and very inspiring too