Sunday, September 16, 2012

IBM's SAGE Computer

This is IBM’s SAGE computer system control console. SAGE or the AN/FSQ-7 & AN/FSQ-8 was a computer system developed in the 50’s by IBM for military use, primarily air traffic control and radar defense.

Four main contractors were responsible for SAGE: IBM for hardware; Burroughs for inter-Center communications, Massachusetts Institute of Technology's Lincoln Laboratories for system integration; Western Electric for design & construction of buildings; and SDC (part of the RAND Corporation) for software. In 1958, the MITRE Corporation was formed out of the Computer System Division of Lincoln Laboratories. Much of MITRE’s initial work focused on the software development of SAGE’s digital computer system, radar surveillance, communications, and weapons integration. More importantly however, MITRE had the role of integrating many elements of the SAGE system

Today MITRE continues as a software engineering think tank, well known for many software process improvements including the CWE or Common Weakness Enumeration that I based a lot of my software quality control efforts and education upon. (

The SAGE system was a continental air-defense network commissioned by the U.S. military. SAGE stood for "Semi-Automatic Ground Environment." SAGE was the most ambitious computer project ever undertaken, The Project required over 800 programmers and the technical resources of some of America's largest corporations.

The total project cost is estimated to have been between 8-12 billion dollars (1964), but that included the construction of 23 concrete-hardened bunkers across the United States (and one in Canada) linked into a continental air-defense system called "SAGE."

SAGE was designed to detect atomic bomb-carrying Soviet bombers and guide American missiles to intercept and destroy them. SAGE was linked to nuclear-tipped Bomarc and Nike missiles. Each of the 23 SAGE "Direction Centers" housed an A/N FSQ-7 computer, the name given to it by the U.S. Military. The SAGE computer system used 3MW of power. It took over 100 people to operate.

It’s specifications would seem competitive today:
  • Dual Processor one on line, other training, maintenance, hot backup
  • Communication to remote sites, flying manned/unmanned vehicles
  • Hot plugable modules, did not have to remove power from the rest of the machine to remove/insert a plug-in module. (An OFF/ON switch for each module.)
  • a 32 bit machine, left half was op code, right half address
It was started in the 1950's and was operational by 1963. It remained in continuous operation until 1983, over 20 years.

The machine’s requirements were so far ahead of the state of the art that it required IBM invent all kinds of new technology, such as pipelined instructions, that is the basis of today’s modern systems. Implementing such advanced architecture with vacuum tubes truly stretched the state of the art.

I feel it directly led IBM to the development of "Project Stretch" and the model 7030. Still, the 7030 just never met expectations and was finally considered a failure by IBM. Ten years later, Tom Watson, Jr. reversed himself and congratulated the designers of Stretch when he realized how it had led to the IBM 360 architecture, the computer family that cemented IBM as the leading mainframe manufacturer of all time and sunk more competitors than Rockefeller and Carnegie combined.

While the IBM 7030 was not considered successful, it spawned many technologies incorporated in future machines that were highly successful. The Standard Modular System transistor logic was the basis for the IBM 7090 line of scientific computers, the IBM 7070 and 7080 business computers, the IBM 7040 and IBM 1400 lines, and the IBM 1620 small scientific computer. (The 7030 used about 170,000 transistors.) The IBM 7302 Model I Core Storage units were also used in the IBM 7090, IBM 7070 and IBM 7080. Multiprogramming, memory protection, generalized interrupts, the 8-bit byte were all concepts later incorporated in the IBM System/360 line of computers as well as most later CPUs.

Stephen Dunwell, the project manager who became a scapegoat when Stretch failed commercially, pointed out soon after the phenomenally successful 1964 launch of System/360 that most of its core concepts were pioneered by Stretch.

By 1966 he had received an apology and been made an IBM Fellow, a high honor that carried with it resources and authority to pursue one's desired research.

Instruction pipelining, prefetch and decoding, and memory interleaving were used in later supercomputer designs such as the IBM System/360 Models 91, 95 and IBM System/370 Model 195, and the IBM 3090 series as well as computers from other manufacturers. As of 2011, these techniques, are still used in most advanced microprocessors starting with the Intel Pentium and the Motorola/IBM PowerPC as well as in many embedded microprocessors and microcontrollers from various manufacturers. All trace their roots back to the IBM work on Stretch and SAGE.

When my dad went back to work as an air traffic controller in 1965, he was stationed at Malmstrom Air Force Base in Great Falls operating a SAGE equipped air traffic system. The Air Force guards still carried automatic weapons since the computer technology was considered top secret.

At 250 tons and 60,000 vacuum tubes, the SAGE system was the largest, heaviest and most expensive computer system ever built!

Think about that as I type this note on a 2.3 pound Mac Air that contains something in the neighborhood of 1,700,000,000 transistors — that's almost 2 TRILLION! We’re living in the future.

The SAGE system used a light pen to identify a radar blip on the screen. The computer would then show flight information for the blip including altitude, heading, identification, and flight plan data.

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