<upsidedown@downunder.com> wrote in message news:3535jf1d6gcioqq6s4ombgffdm8p37prl6@4ax.com...> One thing limiting the speed was the high tube stray capacitances and > high impedance levels. Finding tubes with good cathode emissivity > might help to design logical circuits with low (say 20-30 V) anode > voltages.Usually the voltages are modest (~100V), so that adequate current can be drawn. Low voltage, you need too much cathode area and capacitance, and your figure of merit (Gm/(Cin+Cout), which has units of frequency) stinks. And obviously, the FoM doesn't change with scale (length/area of cathode). Though other fixed parameters (like wiring strays) do affect the FoM in-system, so you don't want to use too small of a tube.> Ordinary tubes can have reassemble power gain in grounded grid > configuration even at VHF. A grounded grid flip-flop ??They can, but not baseband to VHF. Only a few late era planar types could do that. (Which at the time, were more valuable doing the same ~100MHz bandwidth around a center frequency of some GHz -- pretty good bandwidth even today, to be fair!) That's the trick. Example: I happen to have a carton of subminiature (wire lead) 5702s. These are your basic general purpose / RF, sharp cutoff pentode. 1W max, 5mS at 100V, 10mA. In an accidentally-grounded-grid arrangement, these like to oscillate around 400MHz; it's the interelectrode ESL+Cp resonant mode I think. (This might happen accidentally, like in a follower type Hartley oscillator, which places its tuning capacitor between grid and ground.) They're perfectly capable of operating at high frequencies; the transit time is a nanosecond or two. (This can be measured with a very low plate load and a fast pulse generator into the grid. The gain in this configuration is pitiful, obviously, but you can indeed see the current changing in that time!) The capacitances are about 4pF plate and 5pF grid *WHEN COLD*. However the grid capacitance increases when hot -- because the electron cloud has mass, cool huh? -- to more like 9pF. So the total in cascade is 4+9 = 13pF. Plus circuit strays. That gives a FoM = 5mS / (2*pi*13pF) = 61MHz, which is the no-frills (no peaking) ballpark bandwidth, at unity gain (i.e., a 1/5mS = 200ohm plate load). In a practical computer, you'd need 1/2 to 1/3 of this (even for a tiny fanout of, well, about as much), and even with peaking (to about double it, give or take how that works in combination with nonlinear loads like diode gates), you're looking at a maximum clock rate for typical gates of maybe 20MHz. Which, is still pretty promising; that's not much slower than 74HC logic, and faster than CD4000, scarily enough. It does take about a dozen watts to compute even fairly simple logic operations though... ECL's got nothing on this!> Of course some shift registers, such as mercury delay lines or 64 us > PAL TV delay lines might be used.Heh, given that those have been obsolete for a while now too -- not hard to find though. I wonder how much data those store. Let's see, 64us, at a MHz or two bandwidth -- they had to store chroma, modulated I believe, so that's offset on a center frequency? -- suggests 2Mbit/s * 64us = 128 bits. Although that's not actually bits, but baud, and more bits could be encoded given some manner of ADC/DAC system, with adequate SNR and ISI (with whatever ISI compensation can be afforded). Not bad for, like, a register file, or perhaps more practically, a cache line..? And since it's modulated, it needs some encoding. PAM perhaps, which would be an easy enough way to transmit 2 bits/symbol (BPASK I guess you might call it?). Probably it would be easy enough making a 4x4 square constellation (4 bits/symbol) too. Which puts it up around half a kiB, which isn't too shabby. And it would probably match up well enough with a 5702-based (or other tubes of comparable performance) machine. Downside, now you have to "spin the drum" or whatever; efficient programming gets a lot harder... (I wonder if anyone's ever written a compiler/optimizer around such a constraint? Certainly very little reason to do so today, but as an academic exercise, maybe interesting.)> A Teletype terminal al should do. One Teletype we used had only > semiconductor mains rectifiers and a TO3 power transistor in the 20 mA > constant current generator. The data generation and decoding was all > electromechanical.Well, I don't know about that. They certainly worked..when they did. How many of them are even around anymore? And of them, how many are basically in parts, or in need of extreme-teardown levels of maintenance? :^) Definitely mechanical wonders; I've quite enjoyed CuriousMarc's restoration series: https://www.youtube.com/watch?v=_NuvwndwYSY And absolutely, if you have one in working order -- perfectly compatible with the same old serial frames we've always used, if at rather low baud rates. Just insert RS-232 (or TTL, or..) to 20mA converter, and don't touch the high voltages. :) Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website: https://www.seventransistorlabs.com/
Is there a good book for learning about valves/tubes?
Started by ●August 9, 2020
Reply by ●August 11, 20202020-08-11
Reply by ●August 11, 20202020-08-11
On Sunday, August 9, 2020 at 2:06:16 PM UTC-7, david eather wrote:> suggestions please > TIARadiotron for one. Go here and poke around: https://worldradiohistory.com/ for example, try: Technical & Engineering > Technical Books > Rider Book Library https://worldradiohistory.com/BOOKSHELF-ARH/Bookshelf_RIder.htm https://worldradiohistory.com/BOOKSHELF-ARH/Rider-Books/Rider-Inside-the-Vacuum-Tube-1945.pdf
Reply by ●August 11, 20202020-08-11
On 12.08.20 1:50, Simon S Aysdie wrote:> On Sunday, August 9, 2020 at 2:06:16 PM UTC-7, david eather wrote: >> suggestions please >> TIA > > Radiotron for one. > > Go here and poke around: > > https://worldradiohistory.com/ > > for example, try: Technical & Engineering > Technical Books > Rider Book Library > > https://worldradiohistory.com/BOOKSHELF-ARH/Bookshelf_RIder.htm > https://worldradiohistory.com/BOOKSHELF-ARH/Rider-Books/Rider-Inside-the-Vacuum-Tube-1945.pdf >Hmm... Nice pdf. Thanks.
Reply by ●August 11, 20202020-08-11
On Tuesday, 11 August 2020 at 12:39:27 UTC+1, Tim Williams wrote:> "Phil Hobbs" <pcdhSpamM...@electrooptical.net> wrote in message > news:rgsipb$17mk$1...@gioia.aioe.org... > > EMP-proof serial computer, definitely. ;) > Y'know, I wonder what kind of performance one of those could do, given > modern architectural and electronic knowledge. > > A clock frequency somewhat under a MHz seems reasonable, there'd be some > tradeoff between tube count and computational power, and with say 16 bit > instruction cycles and standard integer ops (logic, arithmetic, and since > it's serial, mul and div are pretty cheap) it should be competetive with, > say, the Apollo Guidance Computer (~50kIPS) or some very impoverished MCUs > (maybe not any 8-bit machines, but those 4-bitters that are still around in > some niches). > > The memory of course is always going to be the hard part. If you're > reluctant to patch in a modern SRAM, you're going to have a hard time doing > much of anything else. (Not bad if you find an old core module in working > condition, I guess.) > > But then, you still need all the support hardware to make use of it. Even > just a serial terminal, you either need to get lucky with a surviving > vintage one (where "vintage" in this scenario includes any current tech > that's surviving?), or make one yourself, which means you're going to need a > CRT and support components, rasterizer, character generator, video RAM... > All things which existed in various forms back in the day (delay line might > be okay for the RAM; and there were CRT-ROMs for drawing characters!), but > which weren't exactly corner-store items even back then. > > Probably the more realistic scenario is developing a hack-friendly Android > OS to use on all those phones that are suddenly less useful without active > base stations, and even if a bunch end up dead for various reasons, there's > just so many that will survive. Much easier then to keep the battery > charged, which, automotive and mains chargers are at least as likely to > survive and remain as reliable as they were (which is to say, not always > that much heh, but still), and mains inverters and generators, and car > batteries and alternators, aren't going away ever so that should be a good > enough stopping point. (Engines in turn can be fed by gassified wood, for > example.) > TimWould VFDs be usable for computation? Not just because they're low power & long lived, but also they have matrix-like arrangement of grids & anodes. NT
Reply by ●August 12, 20202020-08-12
On 8/10/20 11:50 PM, Phil Hobbs wrote:> Takes too many tubes. See the IBM 650.So it's technically possible. It's just not practical. -- Grant. . . . unix || die
Reply by ●August 12, 20202020-08-12
On Tue, 11 Aug 2020 18:11:37 -0500, "Tim Williams" <tiwill@seventransistorlabs.com> wrote:> >> Of course some shift registers, such as mercury delay lines or 64 us >> PAL TV delay lines might be used. > >Heh, given that those have been obsolete for a while now too -- not hard to >find though. > >I wonder how much data those store. Let's see, 64us, at a MHz or two >bandwidth -- they had to store chroma, modulated I believe, so that's offset >on a center frequency? -- suggests 2Mbit/s * 64us = 128 bits. Although >that's not actually bits, but baud, and more bits could be encoded given >some manner of ADC/DAC system, with adequate SNR and ISI (with whatever ISI >compensation can be afforded). > >Not bad for, like, a register file, or perhaps more practically, a cache >line..?A serial memory (shift register) is ideal for a serial machines. For addition/subtraction. just use little endian format circulating in two or more shift registers. First, add the LSB from the registers, store the sum into the second (or third) shift register LSB. Store the carry bit into a single (tube) flip-flop. Shift the registers one bit position. Add the next bits and the carry from the carry flip-flop. Continue with next bits. This is how handheld calculators work. Some are pure 1 bit variants or 4 bit (BCD) wide registers are used. The shift register should be as long as the word length (16 to 40 bits) so that the LSB it is ready for the next instruction cycle. The problem with the 64 us delay is that it also sets the machine cycle or just 15625 instructions/second. A 64 to 128 bit capacity is sufficient, since it allows some dead time for instruction decode etc. before next arithmetic operation restarts. A shorter delay time would be desirable (e.g. some mercury delay lines) to allow a shorter instruction cycle.
Reply by ●August 12, 20202020-08-12
On 2020-08-12 00:46, Grant Taylor wrote:> On 8/10/20 11:50 PM, Phil Hobbs wrote: >> Takes too many tubes. See the IBM 650. > > So it's technically possible. It's just not practical.Sure, there's nothing about tubes that makes parallel architectures impossible. You can do a lot of fun stuff that isn't practical. My old colleague Mark Galt, who helped me with my thesis project long ago, did an all-mechanical Nixie tube clock that is a thing of great beauty: <http://markoapparatus.com/portfolio/machine-clock/> I just ran across it yesterday, in fact. Check out the 45-second video. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●August 12, 20202020-08-12
On Tue, 11 Aug 2020 01:50:21 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 2020-08-11 00:40, Grant Taylor wrote: >> On 8/10/20 4:47 PM, Phil Hobbs wrote: >>> EMP-proof serial computer, definitely. ;) >> >> Why does it have to be serial?� Why can't it be parallel? > >Takes too many tubes. See the IBM 650. > >Cheers > >Phil HobbsSome of those tube machines had hardware floating point. -- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
Reply by ●August 12, 20202020-08-12
On 2020-08-12 01:16, jlarkin@highlandsniptechnology.com wrote:> On Tue, 11 Aug 2020 01:50:21 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 2020-08-11 00:40, Grant Taylor wrote: >>> On 8/10/20 4:47 PM, Phil Hobbs wrote: >>>> EMP-proof serial computer, definitely. ;) >>> >>> Why does it have to be serial? Why can't it be parallel? >> >> Takes too many tubes. See the IBM 650.> > Some of those tube machines had hardware floating point.There were giants in those days, for sure. I got to meet one or two of them when I was at IBM, and heard stories about many more. It was much more practical in the old days, when (a) there weren't any good alternatives, and (b) you had your own tube design and manufacturing facility. I don't think anybody makes 6CW4s anymore. This from the inimitable Ken Shirriff: <http://www.righto.com/2018/01/examining-1954-ibm-mainframes-pluggable.html> Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●August 12, 20202020-08-12
On 12/08/20 05:46, Grant Taylor wrote:> On 8/10/20 11:50 PM, Phil Hobbs wrote: >> Takes too many tubes. See the IBM 650. > > So it's technically possible. It's just not practical.The oldest working computer in the world uses dekatrons, valves and relays. https://en.wikipedia.org/wiki/Harwell_computer The Elliott 803 is a serial computer using germanium transistors and magnetic components for the logic. Decca Navigator made a TTL serial computer for avionics applications. They might be a starting point for an architecture. Or you could be seriously radical and build a computer using neon bulbs. I doubt the reliability would be good :)
