How many tubes do I need?
On Thursday, January 31, 2013 4:27:43 PM UTC-5, wrote:
I want to build a computer entirely out of tubes, and be able to
download and store the entire internet on it. How many tubes do I need?
Eniac, the first "practical" digital computer used only tubes as 'switches'.. Something on the order of 17,468 vacuum tubes, 7,200 crystal diodes, 1,500 relays, 70,000 resistors, 10,000 capacitors and around 5 million hand-soldered joints went into the machine. Parts of it still exist at Penn. Its memory was the functional equivalent of about 2300 bits (1.3KB), although there is no actual functional comparison of Core Memory to Flip-Flop memory. It could store (up to) ten (10) signed (+/-) ten-digit numbers, full stop.
It had less computing and/or memory capacity than the Commodore VIC 20. Which had five (5) KB of ram, of which 1.5KB was system memory. Power consumption for the ENIAC was about 160KW/H.
Extrapolating Wildly: If the internet memory capacity is 58 petabytes (each petabyte being 1,000 terabytes) the memory capacity requirement would be quite large - but TUBES did not store the actual data, only processed it. So, you would have to consider the number of tubes to make a reasonable processing time, and the number of tubes, capacitors and flip-flop devices (analog relays) to store the data. Then the power to run it all.
Comes to 10 to the 15KB. 10 to the 42 bytes.
Raw numbers only, and definitely comparing apples (flip-flop) to oranges (core), and all approximations:
Keeping in mind that a typical memory chip has something over (the equivalent of) 40,000,000 discrete components on it, with CPU chips having much, much more, the number of vacuum tubes will be in the several billions. But, for practical purposes, if only one billion tubes are used ENIAC style, that would require, with supporting infrastructure, about 10 MW/H of power, about the equivalent of the entire output of two (2) standard nuclear plants.
2,830,000,000,000 hand-soldered joints (again, assuming ENIAC-style). Assume 10,000 assemblers making 180 joints per hour. That math will be astounding. Not to mention floor-space required, cooling considerations, access, and so on and so forth.
So, the short answer:
More tubes than have been produced world-wide since 1910.
Something far over 2 square miles of footprint. ENIAC was only 1,800 s.f., but remember, access, heat and memory issues using relays.
Interesting exercise in silliness.
Peter Wieck
Melrose Park, PA (and Penn grad).
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