Vacuum Tube Computer P.29 - Addressing and Fanout Problems 

This brings to mind the famous quote from Mr. Spock: "I am attempting to build a mnemonic memory device using stone knives and bear skins"

Yes, more vacuum tube computer content. 😸

This is too funny. I just started watching your channel recently, and hadn't seen any of the VTC videos yet. Watching this one, and I see the instruction set flash by at 3:45, and immediately went "Hey, that's the same as the MC14500B!" I had a mentor that helped me out building a MC14500B system out of the handbook back in the late 70's (probably 1979, specifically).

I hope to see this computer communicate with the centurion someday.

6cg7 is a really good tube. Works great as a phase inverter/splitter or gain stage for audio. Nice to see them in your design

やっぱり、うさぎ電気さんみたいなRU-vidr増えてほしい

i was wondering when you were going to get back to this. its amazing how much space a little memory can take up

Thank a million for the Celsius temps!

somebody mentioned you in the comments of Dave's Garage and I had to comment Usagi is the type of guy I want to be like when i am older :)

This is so great! This is literally how I found you channel.

If it's hot, you can mill at night, no? Start milling and go to sleep. Next day it's done. Love your videos on this vacuum tube computer.

It's always a great day when you post a video! :D

I ask, you deliver! Sir you are a champ.

I LOVE THESE VIDEOS NEVER STOP

Cool project! I wonder why you didn't go with the 6DJ8 instead of the 6CG7 as the cathode-follower. The 6DJ8 has like twice the transconductance which might be helpful. Another possibility might be to go to much higher resistors to the grids of the 6AU6's. If the tubes are not gassy you can probably go up to like 2.2 megohms or so, lowering the DC loading. The slew rate will be slower but you probably are not seeking very high clock speeds. FYI if you think you have logic swing issues, Seymour Cray's mainframe computers had to work with like only 300 millivolts of logic swing, and they worked surprisingly well with that. It required the use of around 35,000 miniature coax cables between the gates, all of them 6 feet long. Regards!

Vintage tech, new projects and animals - a great recipe for me.

22:38: Do you expect me to meow? _No, Mister Neko, I expect you to lie._

Good job!

That is a sweet looking board.

Adding that buffer is gonna slow down your computer!! 🤣🤣

Yes, more quality cat content

WOW! That schematic of the whole memory is FEROCIOUS! Is that drawn by hand or with computer assistance? Either way, it looks just a bit more than a 10 minute job! ;) Before watching this episode I sort-of more-or-less understood how transistor inverters worked but after watching this episode I REALLY get how transistor inverters work. It's funny how I keep learning "transistor stuff" from your videos, y'know considering............

hi my dad worked for the met office in bracknell uk you lot better get used to the hot weather it's going to get a lot more heat going buy the files he was working on there was alot of paper work back in the days and could see what is going on computers came alot and all the eye's could not see it any more love te video's

It's been the kind of summer where you come into the shop to find your solder melted on the floor. Or so it seems haha

Just a comment about cathode followers... They have great rise time, but the fall time is dependent on the load at the cathode, which in your case could be the capacitance of a large number of inputs in parallel with a relatively high cathode resistor. Before you go too far with the next stage I recommend trying the circuit with a clock signal and adding a bunch of capacitance to ground - maybe a few hundred pico-farads. If you have the voltage headroom (you don't) then a mu-follower with some DC level adjustment would possibly be a better choice.

Love it when troubleshooting is that easy! Roughly where in Texas are you? We live about an hour north of Abilene. I agree it has been brutal this past summer and this fall isn't looking much better as far as rainfall.

Put fan on heat sink of you mill and all other places, heatsink is outside the encloser so that is an easy job. :D

Q: about power? > have you thought about how you are going to drive your memory by? Your 1-bit computer is already demanding quit a lot of current, are you going to drive every thing by "one" (1- 12v & 1-24v) Set of power supplies? Or are you going to try to break it up in to one set (1-12v & 1-24v) for the CPU and one set (1-12v & 1-24v) for the memory? have you also thought about how you are going to reset MEM to a known value (for a Reset)? and have you thought about how you are going to make the counter and how you're going to set the counter (for things like jumps, and sub Routines) ? Meaning are you thinking of using a main counter, and a sub routine counter?) Or just one counter ? You already have cut down on how much memory you're going to need by putting in a full ALU unit in the CPU, BUt by having a separate main MEM counter from a Sub routine counter would that not also cut down for the need of a bigger memory? Right now every time you address memory that will take 6 bits to have to store in the counter. Also down the line... Are you going to have to make a 6 bit serial to parallel converter (to load the counters) ? In my ignoance, I am still thinking your going to need more memory, but while I am thinking about that I'm still wondering if Modulizing your memory to smaller packets might be faster? Can your router be run at night or does it need to be Supervised?

Is there scope for using a double triode as two in-series active inverters? Does this provide sufficient improved drive current for the fanout? Or is it too long since I did my electronics training (yes, it was pre-microprocessor days, and did include various valve calculations, but it was a long time ago in a far country etc).

If you want the ultimate in current and low plate resistance for your cathode follower, grab a 6080.

Nice work sir! - what do you do for a living?

I don't think the fan-out is as bad as you are expecting. When more than one input to your NOR gate is high it will effectively draw half the current from each.

I was thinking about this build up to RAM and wondered if you'd ever looked at IBM's "pluggable units?"

Get a swivel knife blade for your CNC and cut vinyl masks and then etch your PCBs... Or do toner transfer or pretty much ANY other method of PCB manufacture vs direct CNC milling and you'll cut down your production time to less than an hour...

I am just getting hooked by your VTC computer series. My training 1968-72 was all solid state, TTL. We had RS flip-flops, you have SR. Did the terminology change from vacuum tube days? Obviously the logic function is the same, just the initials in the opposite order. Your choice of tubes, my, they are all my good friends from youth!

Instead of the 6cg7 it's also possible to use a 12au7 instead. Which works fine on 6V heater. (Heaters in parallel) It's a much smaller tube and much easier to get by. What frequency is the clock running again?

If you want to make boards in summer time, could it be an option to fit the CNC machine with a circuit board marker or other etch resist applier, and etching the board? Just draw it on there like if it's a particularly expensive plotter, then etch it. Those temperatures are ideal for etching boards. Don't even need to heat the bath.

Are ganged triodes ever used for audio circuits to allow smaller tubes to provide more output power?

Great video! Would it be hard to do core memory?

Bletchley Park must be informed about this, it could win WW2.

Whereabouts in Texas are you?

Instinctively I'm pretty sure the logic could be implemented with fewer tubes. Also the 220k grid pulldown to -ve bias seems very low and is unnecessarily loading the previous output, reducing the fanout. Grid leak resistors are typically 1M to 10M, and with such a high bias voltage (-12V) I should think you could use a 10M resistor. Vacuum tubes are voltage operated devices and should not need any significant current on their inputs.

the memory look like a bus based factory in factorio

vacuums for days, nice. Is it concerning at all that the yellow LEDs don't fully power down when you flip the corresponding switches? it's like your "off" state isn't entirely "off"

Why not use a much lower plate resistor for the 6AU6 ?

IMPORTANT: It looks like your leftmost LED is not really switching cleanly between on and off. It seems the yellow one never really goes off while the red one is fainter than the rest. Are you sure the levels are clean and there is no leakage/small short?

I'm sure you thought about this already, could you not use one register divider and hook that output trough the 4.7K registers on pin 1 of the tubes?

On the boards where you need a number of the same type, have you considered one of the Chinese board services? Low cost and good quality. I Use PCB Way.

Always end with kittens👍

What about water cooling the CNC System unit so that it can be used even when it is very hot.

Don't know if you'll get this before a tweet reply I sent today. But I sent you a valve circuit I would love to see built. It may be good for one bit memory. It uses a dual triode, but I'm sure you could make it easily with 6AU6s

"...and then he did a backflip, snapped the bad guys neck and saved the day"

you know the old star trek one the one with all the tubes in it all a round the room funny in away how small things are now ic's came in

After days of binging I have seen episodes 1-29. I read the code for the assembler and want to get more involved. The assembler thus far generates something like micro-code, that is, just the instruction codes. I am interested in going farther with assembler and emulator that will work with the 12-bit instructions so that executable code can be written and tested, ready for UEVTC. In other words, taking the UE14500 assembler and emulator to the UEVTC assembler and emulator. I have joined the discord but don't see an appropriate place to begin this conversation.

Hello, late to the party so please forgive me if this has been answered before: But that mill is gigantic? And, also, since you are going to be making so many PCB why not have a dedicated PCB cutting machine?

wow wow wow! ;)

Hi dude

kool

Four hours! What names did you give your cats? Just don't name one Neko because that would be silly...it would be like naming a rabbit Usagi or a dog Inu (there's a pit bull on RU-vid named that)

is that a commodore monitor behind you????

Great stuff! I'm wondering if you can you build a vacuum tube computer for something like a cell phone with 8 cores and 4GB of RAM?

Thanks for a lot of good videos. Today I vas a litle disapointed only to see a timelapse of your mill. It could be very interesting to have a video about your mill and the tooling you are using. I am tinking about using a mill for pcb prototyping, so it would be very nice to learn from your experiences. Best whishes, and keep up the good work. Chris OZ1GNN

Gotta love that ‘it’s not global warming’ doom and gloom.

wow, what a massive eight bits. thats not a byte thats a whole meal

Don't you just love multiplexing ? LOL. Daft kitties. (as bad as mine. Ha ha)

When i am 50 i want to be like you.

兎はどこですか？

You might want to consider using one of the hobbyist PCB manufacturing companies out there. Just for the time savings.

why use pentodes? you could've cut the tube count in half by using dual-triodes, and you'd also have lower output impedance to cause less problems. there are also soviet micro-tubes which are really cheap, and a bit smaller, if you can get ahold of them.

First 🤣

Why not have the PCB made by a fab? You already proved you can do it yourselves. A PCB house is a lot faster then quitting for the summer because the texan legislature hasn't discovered climate change yet.

I have to say those PCB layouts are really bad, you could've made them much more compact and save manufacture time. I'd suggest looking at hundreds of tube appliance designs and learning the good features of each, in my opinion that's the best way to learn good layout practices!

Are you trying to build a vacuum tube based computer, or a transistor based computer just with transistors replaced with vacuum tubes? For example, the british managed to build a vacuum tube based memory just after WW2, with 2560 bits of memory in a single vacuum tube. en.wikipedia.org/wiki/Williams_tube