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Thread: Early Mainframe Information/Schematics/Dimensions: IBM 727 tape unit

  1. #11
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    The Parametron is a majority-logic device, which makes for some interesting logic concepts.

    https://hardforum.com/threads/gatele...logic.1954426/

  2. #12
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    Yes, 36 bit is probably over-ambitious for a tube based machine! Doable for a discrete transistor system, especially if you can get transistors at a few cents each.
    The B205 would be a thing of wonder; I'm a Lost In Space fan, have been since about 1974, and was always awed by B205's lights.
    The Model 544 Datareader has to be the smartest looking tape unit ever developed.
    The NEC 1100 looks very interesting indeed; Parametron!
    This link from the Computer History Museum has a huge amount of information:
    http://ibm-1401.info/
    Thank you again everyone for your suggestions, now I just need a large warehouse and a few hundred million, to spend...

    Model 544.jpg

  3. #13
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    Quote Originally Posted by FPM-III View Post
    I wonder what the electric bill will be to power and cool a vacuum tube computer.
    Well the Manchester Baby uses 3.5Kw and its about the simplest thing you could build,so thats a real bottom line
    Dave
    G4UGM

    Looking for Analog Computers, Drum Plotters, and Graphics Terminals

  4. #14

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    Use core instead of a Williams tube though, and I expect it would use less.

  5. #15
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    That is an interesting point. The baby is IMHO highly optimised in its use of valves/tubes. It is a single bit serial machine with only a subtract instruction. This means you only need a one-bit subtractor. It actually uses an analog current summing subtractor which further reduces the address count. There is an adder as the program counter needs to be incremented and again that uses analog techniques which reduces the valve count..

    There is only a five bit address so address latch is 10 valves. If you went to core you could dispense with the refresh circuit which would save the 10 valves in it, on the other hand reading core is a destructive process so you would need additional logic to manage that. I can't find a description of a valve computer with core but the Bendix G15 which has a drum, uses about 500 valves which is only 10% fewer valves. However I think that it uses point contact diodes. The Baby uses about 300 valve/tube diodes so if you were prepared to use semiconductor diodes you are down to 250 valves, but the power saving is only about 150 watts as the diode heaters use a lot less power (0.6 watts) versus than the EF50 pentodes which take nearly 2 watts each.

    So I guess you could get it down to 2.5Kw but I would suggest that is the bottom limit...
    Dave
    G4UGM

    Looking for Analog Computers, Drum Plotters, and Graphics Terminals

  6. #16
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    The Bendix G-15 CPU is 115v 38a
    The LGP-30 is shown as 1500W in https://en.wikipedia.org/wiki/LGP-30

    These are the smallest of the 50's general-purpose drum memory tube computers.

    http://ed-thelen.org/comp-hist/BRL2n...dCompSurv.html

    covers most late 50's american systems

  7. #17
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    But that Manchester Baby doesn't run a tape drive, does it? I thought that was a requirement.

  8. #18

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    Quote Originally Posted by Al Kossow View Post
    The LGP-30 is shown as 1500W in https://en.wikipedia.org/wiki/LGP-30
    The LGP-30 I restored plugged into a [US] wall socket, though I don't recall if it had a a 15A or 20A plug (this was back in the 70's and long gone, unfortunately). As I recall, there were some odd interactions which made me think the drum memory had "magical" properties - I started with 2 30's, one with mostly-good electronics and a crashed drum, and another with a decent drum but very corroded electronics. Merging the two was quite the chore.

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