Schematics of Atanasoff-Berry Computer logic circuits?

[William Blair]

> If you are referring to the schematics for the ASM
> (Add-Subtract Mechanism), they are readily available, 
> although not including the values for the resistors
> which determine the logic-gate functions. A scan and my
> re-organised versions are accessible at:
> 
>   http://www.cs.ubc.ca/~hilpert/e/ABC/asm.html

Thanks, that's a really great start.  Prior to seeing your reply to my question, I requested an inter-library loan of the book "The Origins of Digital Computers - Selected Papers" which contains the paper which is excerpted on your excellent ABC site.  Even though that book now looks like it won't provide the details I'd expected, since I won't be using the same voltages as the original circuits were likely using, the exact component values will be different anyway. 

I'm not very familiar with vacuum tube circuit design, but I have a PDF copy of the 1952 USAF technical order TO16-1-255 "Basic Theory and Application of Electron Tubes" which looks like it might be sufficient.  I've built two different 12AU7 dual triode vacuum tube stereo headphone amps from plans which use much lower and, therefore, safer and easier-to-produce voltages (24 - 60V) than were used historically in such circuits.  The required plate voltages for these low-power circuits are produced using simple voltage multipliers attached to commonly available and inexpensive low-voltage transformer secondaries.  Since, in the case of digital logic circuits linearity of operation is not a requirement as it is with audio circuits, even lower voltages might be usable although 24 volts seems to be plenty low enough. 

> I was doing some calculations and experiments with vacuum
> tubes a couple of years ago to recreate an ASM, to figure out 
> what might work for the logic-resistor values (not completed). 
> It would be nice to know what the original values were. 
> 
> If you are referring to the schematics for the entire
> machine, I had the same interest when I was working on writing a
> simulator (also on the web pages) to confirm some aspects of the
> functioning of the machine. I managed to get the simulator
> functioning without them, so didn't feel a dire need to get them,
> although it would still be interesting to see them.
> 
> Sometime after the sim was accessible on the web, I was contacted
> by one of the fellows (Charles Schorb) who had worked on the ABC
> reconstruction and I asked him about schematics. His reply:
>   ...
>   Schematics are a bit hard to come by.  They requested
> that I return all my schematics after leaving the project for 'my
> real job'.  Contact Gary Sleege to see if they have lightened up on
> this restriction.
>   ...
> but I haven't pursued it further.

That's strange that they'd be so restrictive about the distribution of schematics for a machine that has no current value beyond that of a historical curiosity.  I know that there was a legal battle between Mauchly with his ENIAC and Atanasoff with his ABC, but that was decided against Mauchly and claimed that his ENIAC plagiarized concepts used by Atanasoff's ABC which then invalidated Mauchly's earlier patent claim to the first electronic computer.  Since Atanasoff won the case 35 years ago, why would they not willingly release all schematics now?  Strange.

> > but I suspect that since school is not in session, I
> > won't soon get a response.
> 
> (Actually, at universities, when school is not in session
> can be a good time to contact people as the people are less likely
> to be busy with students and teaching responsibilities, at least if
> they're not on vacation.)

Right you are.  I've already received a reply to the effect that he will check with applicable points of contact.  I'll let you know the results.

Thanks,
Bill