Saturday, March 24, 2012

Worlds largest computer




"The AN/FSQ-7 is physically the largest computer ever built, and will likely hold that record for the future. Each machine used 55,000 vacuum tubes, about ½ acre (2,000 m²) of floor space, weighed 275 tons and used up to three megawatts of power.

The Semi-Automatic Ground Environment (SAGE) was an automated control system for tracking and intercepting enemy bomber aircraft used by NORAD from the late 1950s into the 1980s. In later versions, the system could automatically direct aircraft to an interception by sending instructions directly to the aircraft's autopilot.

By the time SAGE was completely operational, the Soviet bomber threat had been replaced by the Soviet missile threat, for which SAGE was entirely inadequate. Nevertheless, SAGE was extremely important; it led to great advances in online systems and interactive computing, real-time computing, and data communications using modems. It is generally considered to be one of the most advanced and successful large computer systems ever developed.

Both MIT and IBM supported the project as contractors. IBM's role in SAGE (the design and manufacture of the AN/FSQ-7 computer, a vacuum tube computer with ferrite core memory based on the never-built Whirlwind II) was an important factor leading to IBM's domination of the computer industry, accounting for more than a half billion dollars in revenue, nearly 10% of IBM's income in the late 1950s.

Prior to the introduction of SAGE, the task of intercepting bombers was becoming increasingly difficult. This was the latest shift in a balance of power that had been see-sawing since the 1930s...
The problem became even more acute if the bombers attacked at low level. Radar is line-of-sight, so by approaching close to the ground they would remain hidden behind the curvature of the Earth until approaching to within a few tens of miles...

It was this problem that particularly bothered Dr. George E. Valley, an MIT physics professor. In order to provide any sort of protection for the entire USA, a series of radar stations would have to span both coasts and across Canada. In the event of a raid, there would simply be far too many reports to be able to successfully guide interception. His solution was automation, connecting all of the radar sites to a computer which would then control all of the incoming and outgoing flow of information...

Production of the resulting machines, known technically as the AN/FSQ-7, was awarded initially to RCA but later given to IBM, who started production in 1958...

The AN/FSQ-7 is physically the largest computer ever built, and will likely hold that record for the future. Each machine used 55,000 vacuum tubes, about ½ acre (2,000 m²) of floor space, weighed 275 tons and used up to three megawatts of power. Although the machines used a large number of vacuum tubes, the failure rate of an individual tube was low due to efforts in quality control and a novel quality assurance system called marginal checking that discovered tubes that were growing weak, before they failed. Each SAGE site included two computers for redundancy, with one processor on "hot standby" at all times. In spite of the poor reliability of the tubes, this dual-processor design made for remarkably high overall system uptime. 99% availability was not unusual.

SAGE sites were connected to multiple radar stations which transmitted tracking data (range and azimuth) in digitized format by modem over ordinary telephone lines. These digitized inputs were automatically prepared from analog radar inputs by the AN/FST-2B (or successor, AN/FYQ-47[4]) at the radar stations. The SAGE computers then collected the tracking data for display on a CRT as icons. Situation Display (SD) console operators at the center could select any of the "targets" on the display with a light gun, and then display additional information about the tracking data reported by the radar stations. Each SD operator console was equipped with an integral cigarette lighter and ashtray...

The total engineering effort for SAGE was immense. Total project cost remains unknown, but estimates place it between 8 and 12 billion 1964 dollars (60--90 billion 2011 dollars), more than the Manhattan Project that developed the nuclear bomb that SAGE defended against..."


Affordable personal computers are now available for most of the world's population.

2 comments:

truthspew said...

Here's some more fascinating information.

The reliability and lifespan of the tubes, that methodology was produced by Bell Labs. In the 1956 Consent Decree they had to start sharing their patents for processes to lengthen the span of time a tube could operate from 41 days to almost 10 years.

The other interesting thing is that by the mid 1950's the transistor was reaching greater numbers for production. I wonder why they chose tubes over the transistor for the SAGE project?

High Power Rocketry said...

Maybe they went with the devil they knew? Spacecraft always seem to use the computer technology of the decade or so before the flight. It is more reliable, and allows for larger CPU processes - making it more robust in radiation environments.

It seems like the conservative choice. Interestingly, computers did not get all that fast until the 1980s. So even years later, this computer could have been replaced by something smaller and faster, but not something very small or very fast.