- A GPU (Graphics Processing Unit) is a processor attached to a graphics card dedicated to calculating floating point operations and the like.
- A graphics accelerator incorporates custom microchips which contain special mathematical operations commonly used in graphics rendering. The efficiency of the microchips therefore determines the effectiveness of the graphics accelerator. They are mainly used for playing 3D games or high-end 3D rendering.
- A GPU implements a number of graphics primitive operations in a way that makes running them much faster than drawing directly to the screen with the host CPU. The most common operations for early 2D computer graphics include the BitBLT operation (combines several bitmap patterns using a RasterOp), usually in special hardware called a "blitter", and operations for drawing rectangles, triangles, circles, and arcs. Modern GPUs also have support for 3D computer graphics, and typically include dig
The ANTIC and CTIA chips provided for hardware control of mixed graphics and text modes, sprite positioning and display (a form of hardware blitting), and other effects on Atari 8-bit computers. The ANTIC chip was a special purpose processor for mapping (in a programmable fashion) text and graphics data to the video output. The designer of the ANTIC chip, Jay Miner, subsequently designed the graphics chip for the Commodore Amiga.ital video–related functions.
The Commodore Amiga was the first mass-market computer to include a blitter in its video hardware, and IBM's 8514 graphics system was one of the first PC video cards to implement 2D primitives in hardware.
The Amiga was unique, for the time, in that it featured what would now be recognized as a full graphics accelerator, offloading practically all video generation functions to hardware, including line drawing, area fill, block image transfer, and a graphics coprocessor with its own (primitive) instruction set. Prior to this (and quite some time after on most systems) a general purpose CPU had to handle every aspect of drawing the display.
In 1991, S3 Graphics introduced the first single-chip 2D accelerator, the S3 86C911 (which its designers named after the Porsche 911 as an indication of the performance increase it promised). The 86C911 spawned a host of imitators: by 1995, all major PC graphics chip makers had added 2D acceleration support to their chips. By this time, fixed-function Windows accelerators had surpassed expensive general-purpose graphics coprocessors in Windows performance, and these coprocessors faded away from the PC market.
Throughout the 1990s, 2D GUI acceleration continued to evolve. As manufacturing capabilities improved, so did the level of integration of graphics chips. Additional application programming interfaces (APIs) arrived for a variety of tasks, such as Microsoft's WinG graphics library for Windows 3.x, and their later DirectDraw interface for hardware acceleration of 2D games within Windows 95 and later.
In the early and mid-1990s, CPU-assisted real-time 3D graphics were becoming increasingly common in computer and console games, which led to an increasing public demand for hardware-accelerated 3D graphics. Early examples of mass-marketed 3D graphics hardware can be found in fifth generation video game consoles such as PlayStation and Nintendo 64. In the PC world, notable failed first-tries for low-cost 3D graphics chips were the S3 ViRGE, ATI Rage, and Matrox Mystique. These chips were essentially previous-generation 2D accelerators with 3D features bolted on. Many were even pin-compatible with the earlier-generation chips for ease of implementation and minimal cost. Initially, performance 3D graphics were possible only with discrete boards dedicated to accelerating 3D functions (and lacking 2D GUI acceleration entirely) such as the 3dfx Voodoo. However, as manufacturing technology again progressed, video, 2D GUI acceleration, and 3D functionality were all integrated into one chip. Rendition's Verite chipsets were the first to do this well enough to be worthy of note.
OpenGL appeared in the early 90s as a professional graphics API, but became a dominant force on the PC, and a driving force for hardware development. Software implementations of OpenGL were common during this time although the influence of OpenGL eventually led to widespread hardware support. Over time a parity emerged between features offered in hardware and those offered in OpenGL. DirectX became popular among Windows game developers during the late 90s. Unlike OpenGL, Microsoft insisted on providing strict one-to-one support of hardware. The approach made DirectX less popular as a stand alone graphics API initially since many GPUs provided their own specific features, which existing OpenGL applications were already able to benefit from, leaving DirectX often one generation behind. (See: Comparison of OpenGL and Direct3D).
Over time Microsoft began to work closer with hardware developers, and started to target the releases of DirectX with those of the supporting graphics hardware. Direct3D 5.0 was the first version of the burgeoning API to gain widespread adoption in the gaming market, and it competed directly with many more hardware specific, often proprietary graphics libraries, while OpenGL maintained a strong following. Direct3D 7.0 introduced support for hardware-accelerated transform and lighting (T&L). 3D accelerators moved beyond being just simple rasterizers to add another significant hardware stage to the 3D rendering pipeline. The NVIDIA GeForce 256 (also known as NV10) was the first card on the market with this capability. Hardware transform and lighting, both already existing features of OpenGL, came to hardware in the 90s and set the precedent for later pixel shader and vertex shader units which were far more flexible and programmable.
2000 to present
With the advent of the OpenGL API and similar functionality in DirectX, GPUs added programmable shading to their capabilities. Each pixel could now be processed by a short program that could include additional image textures as inputs, and each geometric vertex could likewise be processed by a short program before it was projected onto the screen. NVIDIA was first to produce a chip capable of programmable shading, the GeForce 3 (code named NV20). By October 2002, with the introduction of the ATI Radeon 9700 (also known as R300), the world's first Direct3D 9.0 accelerator, pixel and vertex shaders could implement looping and lengthy floating point math, and in general were quickly becoming as flexible as CPUs, and orders of magnitude faster for image-array operations. Pixel shading is often used for things like bump mapping, which adds texture, to make an object look shiny, dull, rough, or even round or extruded. 
As the processing power of GPUs have increased, so has their demand for electrical power. High performance GPUs often consume more energy than current CPUs. See also performance per watt and quiet PC.
Today, parallel GPUs have begun making computational inroads against the CPU, and a subfield of research, dubbed GPGPU for General Purpose Computing on GPU, has found its way into fields as diverse as oil exploration, scientific image processing, linear algebra, 3D reconstruction and even stock options pricing determination. There is increased pressure on GPU manufacturers from "GPGPU users" to improve hardware design, usually focusing on adding more flexibility to the programming model.
Many companies have produced GPUs under a number of brand names. In 2008, Intel, NVIDIA and AMD/ATI were the market share leaders, with 49.4%, 27.8% and 20.6% market share respectively. However, those numbers include Intel's very low-cost, less powerful integrated graphics solutions as GPUs. Not counting those numbers, NVIDIA and AMD control nearly 100% of the market. VIA Technologies/S3 Graphics and Matrox also produce GPUs.
Modern GPUs use most of their transistors to perform calculations related to 3D computer graphics. They were initially used to accelerate the memory-intensive work of texture mapping and rendering polygons, later adding units to accelerate geometric calculations such as the rotation and translation of vertices 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 and interpolation techniques to reduce aliasing, and very high-precision color spaces. Because most of these computations involve matrix and vector operations, engineers and scientists have increasingly studied the use of GPUs for non-graphical calculations.
In addition to the 3D hardware, today's GPUs include basic 2D acceleration and framebuffer capabilities (usually with a VGA compatibility mode). In addition, most GPUs made since 1995 support the YUV color space and hardware overlays (important for digital video playback), and many GPUs made since 2000 support MPEG primitives such as motion compensation and iDCT. Recent graphics cards even decode high-definition video on the card, taking some load off the central processing unit.
Posted by rupesh Sunday, July 5, 2009 at 12:03 AM