„X87“ – Versionsunterschied
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Like other extensions to the basic processor instruction set, these instructions are not strictly needed for programs to work. Instead, they provide hardware support for common mathematical tasks, allowing these tasks to be performed in fewer instructions. For example, the x87 instruction set includes instructions to calculate the [[Trigonometric function|sine]] or [[Trigonometric function|cosine]] of a value. |
Like other extensions to the basic processor instruction set, these instructions are not strictly needed for programs to work. Instead, they provide hardware support for common mathematical tasks, allowing these tasks to be performed in fewer instructions. For example, the x87 instruction set includes instructions to calculate the [[Trigonometric function|sine]] or [[Trigonometric function|cosine]] of a value. |
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All Intel and AMD processors since the [[Intel 80486|80486DX]] have had these instructions built into the main CPU. The term 'x87' is still used to refer to that part of the instruction set that performs conventional floating point operations. |
All Intel and AMD processors since the [[Intel 80486|80486DX]] have had these instructions built into the main CPU. The term 'x87' is still used to refer to that part of the instruction set that performs conventional floating point operations. [[Compiler|compilers]], including [[GNU Compiler Collection|GCC]], may use these instructions to make code that operates faster than if it used library calls to perform floating-point operations. |
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The x87 instructions are compatible with the [[IEEE-754]] standard for floating-point. However, x87 does not perform operations according to strict IEEE-754 formats, since it uses wide registers internally. A given sequence of arithmetic operations may thus behave differently on a x87 and a processor implementing strict IEEE-754 formats.<ref>David Monniaux, ''[http://hal.archives-ouvertes.fr/hal-00128124/en The pitfalls of verifying floating-point computations]'', to appear in ACM TOPLAS</ref> |
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Modern [[Compiler|compilers]], including [[GNU Compiler Collection|GCC]], may use these instructions to make code faster, by performing [[Optimization (computer science)|code optimization]]. |
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==List of x87 generations== |
==List of x87 generations== |
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Version vom 6. Juli 2007, 13:43 Uhr
x87 is a math-related instruction subset of the Intel x86 family line of processors. It is so called because initially such instructions were processed by an external chip with a name ending in 87.
Like other extensions to the basic processor instruction set, these instructions are not strictly needed for programs to work. Instead, they provide hardware support for common mathematical tasks, allowing these tasks to be performed in fewer instructions. For example, the x87 instruction set includes instructions to calculate the sine or cosine of a value.
All Intel and AMD processors since the 80486DX have had these instructions built into the main CPU. The term 'x87' is still used to refer to that part of the instruction set that performs conventional floating point operations. compilers, including GCC, may use these instructions to make code that operates faster than if it used library calls to perform floating-point operations.
The x87 instructions are compatible with the IEEE-754 standard for floating-point. However, x87 does not perform operations according to strict IEEE-754 formats, since it uses wide registers internally. A given sequence of arithmetic operations may thus behave differently on a x87 and a processor implementing strict IEEE-754 formats.[1]
List of x87 generations
- Intel 8087
- Intel 80187
- Intel 80287
- Intel 80387
- Intel 80487 - actually a full-blown 80486DX processor
- NexGen Nx587 - the only member
See also
External link
- ↑ David Monniaux, The pitfalls of verifying floating-point computations, to appear in ACM TOPLAS
