FPU

An abbreviation for "Floating Point Unit". An extra part of the CPU whose sole responsibility is to perform mathematical calculations with fractions and decimals. It handles these calculations a lot faster than the CPU could by itself.

The main usage of the FPU these days is in 3D applications and games, where things like lighting, angles and textures are all calculated with extensive use of the FPU. Even with a 3D-card installed, the FPU still has to calculate lighting and tesselations (with the exception of new "T&L" 3D cards which do this themselves - quickly). Therefore the speed of the FPU has a huge influence on the performance of 3D applications, and is the reason why systems without an FPU, or with a poor FPU (like Cyrix CPUs) are unsuitable for 3D work.