RSS订阅FPU
贡献者：sky2009 浏览：4879次 创建时间：2010-04-09
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FPU：
(Float Point Unit，浮点运算单元)FPU是专用于浮点运算的处理器，以前的FPU是一种单独芯片，在486之后，英特尔把FPU与集成在CPU之内。
A floating point unit (FPU) is a part of a computer system specially designed to carry out operations on floating point numbers. Typical operations are addition, subtraction, multiplication, division, and square root. Some systems (particularly older, microcode-based architectures) can also perform various transcendental functions such as exponential or trigonometric calculations, though in most modern processors these are done with software library routines.
In most modern general purpose computer architectures, one or more FPUs are integrated with the CPU; however many embedded processors, especially older designs, do not have hardware support for floating point operations.
In the past, some systems have implemented floating point via a coprocessor rather than as an integrated unit; in the microcomputer era, this was generally a single microchip, while in older systems it could be an entire circuit board or a cabinet.
Not all computer architectures have a hardware FPU. In the absence of an FPU, many FPU functions can be emulated, which saves the added hardware cost of an FPU but is significantly slower. Emulation can be implemented on any of several levels - in the CPU as microcode, as an operating system function, or in user space code.
In most modern computer architectures, there is some division of floating point operations from integer operations. This division varies significantly by architecture; some, like the Intel x86 have dedicated floating point registers, while some take it as far as independent clocking schemes.
Floating point operations are often pipelined. In earlier superscalar architectures without general out-of-order execution, floating point operations were sometimes pipelined separately from integer operations. Today, many CPUs/architectures have more than one FPU, such as the PowerPC 970, and processors based on the Netburst and AMD64 architectures (such as the Pentium 4 and Athlon 64, respectively.)
When a CPU is executing a program that calls for a floating-point operation, there are 3 ways to carry it out:
a floating point unit emulator (a floating-point library)
add-on FPU
integrated FPU
Most modern computers have integrated FPU hardware
FPU：
"FPU" is short for Formed Police Unit
以下由translator-internet自动翻译，如看不太懂，请寻找近义词
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译文如下：
浮动小数点单位(FPU)是特别地被设计的计算机系统的部分执行在浮动小数点数字的操作。 典型的操作是加法、减法、增殖、分裂和方根。 一些系统(特别更老，基于微指令建筑学)在这些做与软件库惯例的多数现代处理器可也执行各种各样的超越函数例如指数或三角演算，虽则。
在多数现代通用计算机建筑学，一个或更多FPUs集成与CPU; 然而许多嵌入处理器，特别是更旧的设计，没有硬件支持浮动小数点操作。
以前，有些系统通过共处理器实施了浮动小数点而不是作为一个联合单位; 在微型计算机时代，而在更旧的系统它可能是一张整个电路板或内阁，这通常是唯一微集成电路。
不是所有的计算机体系结构有硬件FPU。 在没有FPU时，许多FPU作用可以看齐，节省FPU的增加的硬件费用，但是显着更慢的。 仿效在可以被实施任何几个水平-在CPU作为微指令，比如一个操作系统的作用，或者用用户空间代码。
在多数现代计算机体系结构，有浮动小数点操作一些分裂从整数操作的。 这分裂由建筑学极大变化; 而一些采取它就独立计时的计划，一些，象英特尔x86致力了浮动小数点记数器。
浮动小数点操作经常用管道运输。 在没有一般故障中施行的更早的superscalar建筑学，浮动小数点操作分别地有时用了管道运输与整数操作。 今天，许多CPUs或建筑学有超过一根据Netburst和AMD64建筑学的FPU，例如PowerPC 970和处理器(例如奔腾4和Athlon 64，分别。)
当CPU执行要求一个浮点运算的一个节目时，有3种方式运载它：
浮动小数点单位仿真器(一个浮点图书馆)
添加FPU
联合FPU
多数现代计算机集成了FPU硬件
FPU ：
“FPU”为被形成的警察小分队是短的
开放分类
参考资料
http://baike.baidu.com/view/188677.htm
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