# How Many Vaccuum Tubes to Build a Computer? **URL:** \ **Category:** Factual Questions\ **Created:** [February 5, 2007, 6:56pm UTC](https://boards.straightdope.com/t/how-many-vaccuum-tubes-to-build-a-computer/390967 "2007-02-05T18:56:52Z")\ **Posts on this page:** 6\ **Page:** 2
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 5, 2007, 11:34pm UTC](https://boards.straightdope.com/t/how-many-vaccuum-tubes-to-build-a-computer/390967/21 "2007-02-05T23:34:48Z")
> [@](#): > > I wonder if any slide rules have ever flown in space. On all the early Russian missions, so far as I know. One piece of standard equiment for cosmonauts was a wristwatch with a built-in circular slide rule. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [February 6, 2007, 12:04am UTC](https://boards.straightdope.com/t/how-many-vaccuum-tubes-to-build-a-computer/390967/22 "2007-02-06T00:04:45Z")
[QUOTE=Voyager] We aren’t? Sure could have fooled our technology group. 🙂 **yabob** , could you give me a cite for a computer implemented with physical relays, not relay like structures implemented by vaccuum tubes? I guess phone switches, if considered as computers, might be one example. [/QUOTE] The [cryptanalytic bombes](http://en.wikipedia.org/wiki/Bombe) that broke the Enigma codes in World War II were simply rotors and relays. Plus a huge amount of ingenuity and wire. ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [February 6, 2007, 12:19am UTC](https://boards.straightdope.com/t/how-many-vaccuum-tubes-to-build-a-computer/390967/23 "2007-02-06T00:19:57Z")
The SAGE units were still in operation when my wife worked at the AF Base Library about 800 feet from one such building, in the mid 1970s. Imagine a three-story blockhouse, square in footprint and perhaps 500 feet on a side, full of nothing but vacuum tube computer (plus spare parts and working areas for the technicians attending it). And the net memory available to this behemoth? A whopping 64KB!! ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [February 6, 2007, 12:34am UTC](https://boards.straightdope.com/t/how-many-vaccuum-tubes-to-build-a-computer/390967/24 "2007-02-06T00:34:12Z")
[QUOTE=GorillaMan] Fascinating links - I particularly like [this](http://www.smecc.org/IBM/tomsage.jpg) picture. My father loves to ridicule the ‘flashing-lights consoles’ of old sci-fi films and programmes. That photo shows one in real life. (And in the context of this thread, I guess the flashing lights, or lack of flashing, could help pinpoint dud tubes?) [/QUOTE] [Here’s a page dedicated to the use of the SAGE parts in various sci-fi films.](http://ripsaw.cac.psu.edu/~mloewen/Q7/) ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [February 6, 2007, 1:17am UTC](https://boards.straightdope.com/t/how-many-vaccuum-tubes-to-build-a-computer/390967/25 "2007-02-06T01:17:44Z")
I’m truly amazed by those uses of SAGE apparatus in TV series and movies – I felt sure that the stuff on the Seaview was all made-up malarky, but apparently they use real military computer hardware. No wonder most of the Visions of the Future look the same! I’m truly amazed at the fact that ABC News as recently as 1996 stuck old SAGE parts “for show” on the set. One place that _didn’t_ use old SAGE hardware was the original version of **The Fly** – it was still being developed and used back then. I remember sitting at a screening at MIT and listening to the old computer hands behind me arguing about which hardware that really was in David Hedison’s lab. ---
**Author:** ![danceswithcats](https://avatars.discourse-cdn.com/v4/letter/d/9e8a1a/32.png) [@danceswithcats](https://boards.straightdope.com/u/danceswithcats)\ **Post date:** [February 6, 2007, 1:21am UTC](https://boards.straightdope.com/t/how-many-vaccuum-tubes-to-build-a-computer/390967/26 "2007-02-06T01:21:18Z")
[The story of ENIAC](http://ftp.arl.mil/~mike/comphist/eniac-story.html), which used 19,000 vacuum tubes and 1,500 relays. [Previous page](https://boards.straightdope.com/t/how-many-vaccuum-tubes-to-build-a-computer/390967.md?page=1)