Monday, December 22, 2008

pentium flaw

Main article: Pentium FDIV bug

Intel engineers discovered a flaw in the floating-point math subsection of the Pentium microprocessor. Under certain data dependent conditions, low order bits of the result of floating-point division operations would be incorrect, an error that can quickly compound in floating-point operations to much larger errors in subsequent calculations. Intel corrected the error in a future chip revision, but nonetheless declined to disclose it.

Dr. Thomas Nicely, Professor of Mathematics at Lynchburg College independently discovered the bug, and upon receiving no response from his inquiry to Intel, on October 30 posted a message on the Internet.[18] Word of the bug spread quickly on the Internet and then to the industry press. Because the bug was easy to replicate by an average user (there was a sequence of numbers one could enter into the OS calculator to show the error), Intel's statements that it was minor and "not even an erratum" were not accepted by many computer users. During Thanksgiving 1994, The New York Times ran a piece by journalist John Markoff spotlighting the error. Intel changed its position and offered to replace every chip, quickly putting in place a large end-user support organization. This resulted in a $500 million charge against Intel's 1994 revenue.

Ironically, the "Pentium flaw" incident, Intel's response to it, and the surrounding media coverage propelled Intel from being a technology supplier generally unknown to most computer users to a household name. Dovetailing with an uptick in the "Intel Inside" campaign, the episode is considered by some to have been a positive event for Intel, changing some of its business practices to be more end-user focused and generating substantial public awareness, while avoiding (for most users) a lasting negative impression.

386 microprocessor


During this period Andrew Grove dramatically redirected the company, closing much of its DRAM business and directing resources to the microprocessor business. Of perhaps greater importance was his decision to "single-source" the 386 microprocessor. Prior to this, microprocessor manufacturing was in its infancy, and manufacturing problems frequently reduced or stopped production, interrupting supplies to customers. To mitigate this risk, these customers typically insisted that multiple manufacturers produce chips they could use to ensure a consistent supply. The 8080 and 8086-series microprocessors were produced by several companies, notably Zilog and AMD. Grove made the decision not to license the 386 design to other manufacturers, instead producing it in three geographically distinct factories in Santa Clara, California; Hillsboro, Oregon; and the Phoenix, Arizona suburb of Chandler; and convincing customers that this would ensure consistent delivery. As the success of Compaq's Deskpro 386 established the 386 as the dominant CPU choice, Intel achieved a position of near-exclusive dominance as its supplier. Profits from this funded rapid development of both higher-performance chip designs and higher-performance manufacturing capabilities, propelling Intel to a position of unquestioned leadership by the early 1990s.

486, Pentium, and Itanium

Intel introduced the 486 microprocessor in 1989, and in 1990 formally established a second design team, designing the processors code-named "P5" and "P6" in parallel and committing to a major new processor every two years, versus the four or more years such designs had previously taken. The P5 was earlier known as "Operation Bicycle" referring to the cycles of the processor. The P5 was introduced in 1993 as the Intel Pentium, substituting a trademarked name for the former part number (numbers, like 486, cannot be trademarked). The P6 followed in 1995 as the Pentium Pro and improved into the Pentium II in 1997. New architectures were developed alternately in Santa Clara, California and Hillsboro, Oregon.

The Santa Clara design team embarked in 1993 on a successor to the x86 architecture, codenamed "P7". The first attempt was dropped a year later, but quickly revived in a cooperative program with Hewlett-Packard engineers, though Intel soon took over primary design responsibility. The resulting implementation of the IA-64 64-bit architecture was the Itanium, finally introduced in June 2001. The Itanium's performance running legacy x86 code did not achieve expectations, and it failed to effectively compete with 64-bit extensions to the original x86 architecture, first from AMD (the AMD64), then from Intel itself (the Intel 64 architecture, formerly known as EM64T). As of November 2007, Intel continues to develop and deploy the Itanium.

The Hillsboro team designed the Willamette processor (code-named P67 and P68) which was marketed as the Pentium 4, and later developed the 64-bit extensions to the x86 architecture, present in some versions of the Pentium 4 and in the Intel Core 2 chips. Many chip variants were developed at an office in Haifa, Israel.

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