6. Wall Street Crash (1987)
Cost: $500 billion in one day
Disaster: On “Black Monday” (October 19, 1987), the Dow Jones Industrial Average plummeted 508 points, losing 22.6% of its total value. The S&P 500 dropped 20.4%. This was the greatest loss Wall Street ever suffered in a single day.
Cause: A long bull market was halted by a rash of SEC investigations of insider trading and by other market forces. As investors fled stocks in a mass exodus, computer trading programs generated a flood of sell orders, overwhelming the market, crashing systems and leaving investors effectively blind. (more)
7. AT&T Lines Go Dead (1990)
Cost: 75 million phone calls missed, 200 thousand airline reservations lost
Disaster: A single switch at one of AT&T’s 114 switching centers suffered a minor mechanical problem and shut down the center. When the center came back up, it sent a message to other switching centers, which in turn caused them to shut down and brought down the entire AT&T network for 9 hours.
Cause: A single line of buggy code in a complex software upgrade implemented to speed up calling caused a ripple effect that shut down the network. (more)
8. Patriot Fails Soldiers (1991)
Cost: 28 soldiers dead, 100 injured
Disaster: During the first Gulf War, an American Patriot Missile system in Saudi Arabia failed to intercept an incoming Iraqi Scud missile. The missile destroyed an American Army barracks.
Cause: A software rounding error incorrectly calculated the time, causing the Patriot system to ignore the incoming Scud missile. (more)
9. Pentium Fails Long Division (1993)
Cost: $475 million, corporate credibility
Disaster: Intel’s highly-promoted Pentium chip occasionally made mistakes when dividing floating-point numbers within a specific range. For example, dividing 4195835.0/3145727.0 yielded 1.33374 instead of 1.33382, an error of 0.006%. Although the bug affected few users, it become a public relations nightmare. With an estimated 5 million defective chips in circulation, Intel offered to replace Pentium chips only for consumers who could prove they needed high accuracy. Eventually Intel replaced the chips for anyone who complained.
Cause: The divider in the Pentium floating point unit had a flawed division table, missing about five of a thousand entries and resulting in these rounding errors. (more)
10. Ariane Rocket Goes Boom (1996)
Cost: $500 million
Disaster: Ariane 5, Europe’s newest unmanned rocket, was intentionally destroyed seconds after launch on its maiden flight. Also destroyed was its cargo of four scientific satellites to study how the Earth’s magnetic field interacts with solar winds.
Cause: Shutdown occurred when the guidance computer tried to convert the sideways rocket velocity from 64-bits to a 16-bit format. The number was too big, and an overflow error resulted. When the guidance system shut down, control passed to an identical redundant unit, which also failed because it was running the same algorithm. (more)
Article published on February 12, 2008
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