Graphics processing unit
A Graphics Processing Unit or GPU, also called Visual Processing Unit or VPU is the microprocessor of a graphics card (or graphics accelerator). Modern GPUs are very efficient at manipulating and displaying computer graphics.
The name Graphics Processing Unit for this processor type was originally coined by NVIDIA Corporation by analogy with CPU to refer to its GeForce3 graphics card; in response, ATI Technologies coined their counter-term Visual Processing Unit. The term GPU can now stand for the processor(s) present in all recent graphics cards.
The GPUs developed from the graphics chips. While early graphics chips would be relatively simple hardware units with simple memory mapped control ports and sometimes memory-mapped bitmaps, the graphics processing units introduced an independent programming capability, beginning with the BitBLT operation found in the Xerox Alto computer, and were initially called "blitters". Sometimes, the blitter in the Amiga's chipsets are confused with the "Copper." The Agnus chip supported not only the blitter, but also a video timing coprocessor, named "Copper" for short. The Copper and the Blitter are not the same thing.
Typical operations of early GPUs included moving a section of core memory to the video memory to position it on the screen, and to handle independent graphics blocks, so-called "sprites". Over time, GPUs took on additional functions as software applications and computer interfaces made more extensive use of graphics.
Modern GPUs use most of their transistors to do calculations related to 3D computer graphics. They began by accelerating the memory intensive work of texture mapping and rendering polygons, and later added units to accelerate geometry calculations such as mapping vertex into different coordinate systems. Recent developments in GPUs include support for programmable shaders which can manipulate vertices and textures with many of the same operations supported by CPUs, oversampling techniques to reduce aliasing, and very high-precision color formats. Because most of these computations involve matrix and vector operations, engineers and scientists have increasingly studied using GPUs for non-graphical calculations.
The typical modern stand-alone GPU sits on a separate graphics card from the motherboard, connected to the CPU and main RAM through the AGP or PCI-Express bus. It has access to RAM on the card which is usually faster but lower-capacity than the main RAM. On the other hand, many motherboards have a GPU integrated into the Northbridge that uses the main memory as a frame buffer. This will usually be a cheaper solution than an independent GPU but will have dramatically lower performance. Integrated motherboards may or may not have an AGP slot for a stand-alone graphics card.
GPU manufacturers
See also
