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IBM's $10 Billion Machine

IBM’s SAGE is a large semi-automated air defense system from the Cold War era. It would analyze radar data in real-time to identify Soviet bombers. And it has built-in cigarette lighters and ashtrays at each console. It is the subject of Puzzle 47.


Here you can see about half of the wall of vacuum tubes; the other half could not fit in the frame.


Weight: 300 tons

Cost: ~$10B

This “company-making” sale was made personally by IBM founder Tom Watson, Sr.

Built in 1954, deployed in 1958, obsolete by 1960.


The last of 27 installations was shut down in 1983 (in Canada). In the final years, to the chagrin of the USAF, replacement vacuum tubes had to be bought from Soviet bloc countries.


The software development “employed about 20% of the world’s programmers at the peak of the project. When it was complete, the 250,000 lines of code was the most complex piece of software in existence.” (Computer History Museum details)


Update from below: I just met with a former IBM exec who remembers this program well.


The debug protocol was poetic. Downtime was common. The diagnostic steps were:


1) Visualize it. With the room lights off, the active tubes could be seen glowing. A dark patch was indicative of a power rail connector problem.


2) Listen to the technology. Each of the SLT logic modules were wired through an OR gate and connected to an audio amp. So, as each logic module fired, it added to the acoustic summation. The engineers would listen to the song of the computer and could often recognize common variations.


3)Whack a Mole. If the acoustic pattern seemed erratic, out comes the rubber hammer. Each of the circuit modules would receive a hammer tap to see if the song remains the same. If it changed, then that indicated a loose connector had just been banged back into place.


A fascinating exercise in pattern recognition across the emergent melodies of complex systems...

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Taken on April 21, 2005