SAGE (Semi-Automatic Ground Environment), arsTECHNICA article, 1/4/2022, by Frank O'Brien

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Here's a somewhat thorough article about SAGE, the "Semi-Automatic Ground Environment" system co-ordinating air defense over North America from 1958, parts of it surviving operational up until the early 1980s.

https://arstechnica.com/science/2022/01/the-most-important-computer-youve-never-heard-of/
I searched the forum but could not find a dedicated thread on the subject. Still, I decided to post the link here (in this section) as there are numerous mentions of SAGE in this forum but scattered all over different discussions. I don't know if there's enough there to pull it all together yet, my impression being that it's unlikely as the context of the references varied widely.
 
I've been inside the ex-SAGE building on Luke AFB many times now. It has been converted into an office building that contains many of the base's administrative functions. It's still a windowless concrete bunker however. The people that work there refer to it variously as "The Big Ugly" or "The Blockhouse."

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The building today

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SAGE electronics back when it was operational

https://www.radomes.org/museum/parsehtml.php?html=sagedocs.html&type=base_htmlhttps://www.ibm.com/ibm/history/ibm100/us/en/icons/sage/
 
One of the interesting things with SAGE is that the computer it came from, Whirlwind, used the first every solid-state memory in the form of induction coils on a grid. This reduced the size of a single bit to about 10% of what it was initially, and then to about 1% of it compared to previous vacuum tubes.

whirlwind-core-memory-l.jpg


mit-whirlwind-core-memory-l.jpg


This meant that for the first time it was possible to process in real time radar and other tracking information, integrate it into a plot for intercept and then use that to guide a missile or interceptor to an intercept point on a continent-wide air defense system. Data was transmitted by twisted pair phone lines across the US.

This amounted to the first time something like the Internet existed, even if it was for a specialized purpose.
 

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