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What's an FPU?

The first 680x0 processors (upto 68030) could process integers only. Floating point operations had to be emulated by the software. An FPU is a chip (or part of a chip) that can process floating point operations, a mathematical coprocessor.

One separates three FPU types on the Amiga: The 68881, 68882 and the 68040's internal FPU. The 68882 is up to 1.5 times faster than the 68881, because it is splitted in two parts: A conversion unit (the FPU's are using an 80 bit format internally) and the arithmetic unit. The 68040's internal FPU adds a pipeline, but misses the trigonometric instructions of the others. These are still emulated by the software, 68040.library for example.

Special programs (Raytracing, DTP, Mathematics, TeX) are offered in a special coprocessor version which are up to 50 times faster than the original versions.

Michael Kaiser (kaiser@ira.uka.de)

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