3 ms·

Allegedly, there were just 15 flip-flops, which are reused a lot…

kragen 7y ago
Probably being bit-serial and storing the CPU registers on the drum helped a lot with this. Have you looked at the magnetostrictive-delay-line calculators from the mid-1960s, which used pulses of torsion in a coil of straight-annealed wire instead of a mechanical drum?
- masswerk 7y ago
  In fact, I just have "Electronic Computers" by S.H. Hollingdale and G.C. Toothill (Pelican / Penguin Books, 1965) besides me. While meant to be popular or introductory to the EE side of computing, this is a wonderful book full of such things! Highly recommended and cheap to pick up on various market places!
  - kragen 7y ago
    Thank you for the recommendation! It doesn't seem to be on Libgen or in the Archive's texts collection, and I doubt that I can find a paper copy here in Argentina. Maybe you could scan and upload it; it is presumably in the public domain if it was originally published in the US, since the authors probably did not bother to renew the copyright.
    - masswerk 7y ago
      I picked mine up at abebooks.co.uk – it seems to have been quite popular in the UK at the time. Regarding copyright: It was published in the UK. So for the moment EU copyright regulations, 70 years from the death of the author (I guess).
masswerk 7y ago
Here's I found a source for this: Stanley P. Frankel on the design of MINAC and the LGP-30 in IRE Transactions on Electronic Computers. (15 flip-flops, presenting both normal and inverted output to a logical network made of resistors and crystal diodes, providing basic monotonic Boolean functions like And, Or, and Xor.) Stanley P. Frankel, “The Logical Design of a Simple General Purpose Computer” in: IRE Transactions on Electronic Computers, March 1957, pp. 5 [1] [1] https://www.masswerk.at/nowgobang/misc/MINAC-IRE-March-1957.pdf https://www.masswerk.at/nowgobang/misc/MINAC-IRE-March-1957....
- masswerk 7y ago
  Here's a photo (by Cory Heisterkamp) showing the logic networks from the Ed Thelen's website [1]: http://ed-thelen.org/comp-hist/images/Heistercamp-lgp.jpg http://ed-thelen.org/comp-hist/images/Heistercamp-lgp.jpg (The cards with the rest of the logic are behind and below the main network plane. Mind that this a Control Data model, so it's 1965 or later.) [1] http://ed-thelen.org/comp-hist/lgp-30.html http://ed-thelen.org/comp-hist/lgp-30.html
- kragen 7y ago
  This is awesome! Thank you! This should make the Boolean equations in the manual quite a bit easier to decipher. XOR isn't monotonic — you can't make X ⊕ Y with diode logic given just X and Y, the way you can make X ∧ Y and X ∨ Y. However, you can make it given X, Y, X̄, and Ȳ. I'm not sure if you can make it with X, Y, and just one of X̄ or Ȳ.
  - masswerk 7y ago
    Regarding XOR: This is sloppy quoting of Frankel, who writes about the monotonic functions "And and (nonexclusive) Or" – so, yes, inclusive Or only. However, as described, both the normal and the inverted (negated) outputs of the flip-flops ("toggles") are fed into the network, so there's X and Y and negated X and negated Y available.
    - kragen 7y ago
      Right, and as I explained at https://news.ycombinator.com/item?id=20488446 https://news.ycombinator.com/item?id=20488446, if you have negated versions of all the literals available, you can make not just XOR but any arbitrary Boolean function as a sum of products (or a product of sums, CNF), just like a PLD does.
      - masswerk 7y ago
        Notably, you need XOR (single-bit add) for an ALU anyway… (So the somewhat weak exclusion of "exclusive" in Frankel's paper is a bit luxurious.)

Probably being bit-serial and storing the CPU registers on the drum helped a lot with this. Have you looked at the magnetostrictive-delay-line calculators from the mid-1960s, which used pulses of torsion in a coil of straight-annealed wire instead of a mechanical drum?

masswerk 7y ago
In fact, I just have "Electronic Computers" by S.H. Hollingdale and G.C. Toothill (Pelican / Penguin Books, 1965) besides me. While meant to be popular or introductory to the EE side of computing, this is a wonderful book full of such things! Highly recommended and cheap to pick up on various market places!
- kragen 7y ago
  Thank you for the recommendation! It doesn't seem to be on Libgen or in the Archive's texts collection, and I doubt that I can find a paper copy here in Argentina. Maybe you could scan and upload it; it is presumably in the public domain if it was originally published in the US, since the authors probably did not bother to renew the copyright.
  - masswerk 7y ago
    I picked mine up at abebooks.co.uk – it seems to have been quite popular in the UK at the time. Regarding copyright: It was published in the UK. So for the moment EU copyright regulations, 70 years from the death of the author (I guess).

masswerk 7y ago

Here's I found a source for this: Stanley P. Frankel on the design of MINAC and the LGP-30 in IRE Transactions on Electronic Computers. (15 flip-flops, presenting both normal and inverted output to a logical network made of resistors and crystal diodes, providing basic monotonic Boolean functions like And, Or, and Xor.) Stanley P. Frankel, “The Logical Design of a Simple General Purpose Computer” in: IRE Transactions on Electronic Computers, March 1957, pp. 5 [1] [1] https://www.masswerk.at/nowgobang/misc/MINAC-IRE-March-1957.pdf https://www.masswerk.at/nowgobang/misc/MINAC-IRE-March-1957....

masswerk 7y ago
Here's a photo (by Cory Heisterkamp) showing the logic networks from the Ed Thelen's website [1]: http://ed-thelen.org/comp-hist/images/Heistercamp-lgp.jpg http://ed-thelen.org/comp-hist/images/Heistercamp-lgp.jpg (The cards with the rest of the logic are behind and below the main network plane. Mind that this a Control Data model, so it's 1965 or later.) [1] http://ed-thelen.org/comp-hist/lgp-30.html http://ed-thelen.org/comp-hist/lgp-30.html
kragen 7y ago
This is awesome! Thank you! This should make the Boolean equations in the manual quite a bit easier to decipher. XOR isn't monotonic — you can't make X ⊕ Y with diode logic given just X and Y, the way you can make X ∧ Y and X ∨ Y. However, you can make it given X, Y, X̄, and Ȳ. I'm not sure if you can make it with X, Y, and just one of X̄ or Ȳ.
- masswerk 7y ago
  Regarding XOR: This is sloppy quoting of Frankel, who writes about the monotonic functions "And and (nonexclusive) Or" – so, yes, inclusive Or only. However, as described, both the normal and the inverted (negated) outputs of the flip-flops ("toggles") are fed into the network, so there's X and Y and negated X and negated Y available.
  - kragen 7y ago
    Right, and as I explained at https://news.ycombinator.com/item?id=20488446 https://news.ycombinator.com/item?id=20488446, if you have negated versions of all the literals available, you can make not just XOR but any arbitrary Boolean function as a sum of products (or a product of sums, CNF), just like a PLD does.
    - masswerk 7y ago
      Notably, you need XOR (single-bit add) for an ALU anyway… (So the somewhat weak exclusion of "exclusive" in Frankel's paper is a bit luxurious.)