Floating point unit

A floating-point unit (FPU, colloquially a math coprocessor) is a part of a computer system specially designed to carry out operations on floating point numbers. Typical operations are addition, subtraction, multiplication, division, square root, and bitshifting. 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 general purpose computer architectures, one or more FPUs may be integrated as execution units within the central processing unit; however many embedded processors do not have hardware support for floating-point operations.

When a CPU is executing a program that calls for a floating-point operation, there are three ways to carry it out:

Some systems implemented floating point via a coprocessor rather than as an integrated unit. This could be a single integrated circuit, an entire circuit board or a cabinet. Where floating-point calculation hardware has not been provided, floating point calculations are done in software, which takes more processor time but which avoids the cost of the extra hardware. For a particular computer architecture, the floating point unit instructions may be emulated by a library of software functions; this may permit the same object code to run on systems with or without floating point hardware. Emulation can be implemented on any of several levels: in the CPU as microcode (not a common practice), as an operating system function, or in user space code. When only integer functionality is available the CORDIC floating point emulation methods are most commonly used.

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