Graphics Processing Unit (GPU)

A Graphics Processing Unit (GPU) is a microprocessor that has been designed specifically for the processing of 3D graphics. The processor is built with integrated transform, lighting, triangle setup/clipping, and rendering engines, capable of handling millions of math-intensive processes per second. GPUs allow products such as desktop PCs, portable computers, and game consoles to process real-time 3D graphics that only a few years ago were only available on high-end workstations. Used primarily for 3-D applications, a graphics processing unit is a single-chip processor that creates lighting effects and transforms objects every time a 3D scene is redrawn. These are mathematically-intensive tasks, which otherwise, would put quite a strain on the CPU.

             The functional purpose of a GPU then, is to provide a separate dedicated graphics resources, including a graphics processor and memory, to relieve some of the burden off of the main system resources, namely the Central Processing Unit, Main Memory, and the System Bus, which would otherwise get saturated with graphical operations and I/O requests. The abstract goal of a GPU, however, is to enable a representation of a 3D world as realistically as possible. So these GPUs are designed to provide additional computational power that is customized specifically to perform these 3D tasks.

What’s a GPU????

              A Graphics Processing Unit (GPU) is a microprocessor that has been designed specifically for the processing of 3D graphics. The processor is built with integrated transform, lighting, triangle setup/clipping, and rendering engines, capable of handling millions of math-intensive processes per second. GPUs form the heart of modern graphics cards, relieving the CPU (central processing units) of much of the graphics processing load. GPUs allow products such as desktop PCs, portable computers, and game consoles to process real-time 3D graphics that only a few years ago were only available on high-end workstations.

                Used primarily for 3-D applications, a graphics processing unit is a single-chip processor that creates lighting effects and transforms objects every time a 3D scene is redrawn. These are mathematically-intensive tasks, which otherwise, would put quite a strain on the CPU. Lifting this burden from the CPU frees up cycles that can be used for other jobs.

            However, the GPU is not just for playing 3D-intense videogames or for those who create graphics (sometimes referred to as graphics rendering or content-creation) but is a crucial component that is critical to the PC's overall system speed. In order to fully appreciate the graphics card's role it must first be understood.

                Many synonyms exist for Graphics Processing Unit in which the popular one being the graphics card .It’s also known as a video card, video accelerator, video adapter, video board, graphics accelerator, or graphics adapter.

History and Standards

          The first graphics cards, introduced in August of 1981 by IBM, were monochrome cards designated as Monochrome Display Adapters (MDAs). The displays that used these cards were typically text-only, with green or white text on a black background. Color for IBM-compatible computers appeared on the scene with the 4-color Hercules Graphics Card (HGC), followed by the 8-color Color Graphics Adapter (CGA) and 16-color Enhanced Graphics Adapter (EGA). During the same time, other computer manufacturers, such as Commodore, were introducing computers with built-in graphics adapters that could handle a varying number of colors.

          When IBM introduced the Video Graphics Array (VGA) in 1987, a new graphics standard came into being. A VGA display could support up to 256 colors (out of a possible 262,144-color palette) at resolutions up to 720x400. Perhaps the most interesting difference between VGA and the preceding formats is that VGA was analog, whereas displays had been digital up to that point. Going from digital to analog may seem like a step backward, but it actually provided the ability to vary the signal for more possible combinations than the strict on/off nature of digital.

          Over the years, VGA gave way to Super Video Graphics Array (SVGA). SVGA cards were based on VGA, but each card manufacturer added resolutions and increased color depth in different ways. Eventually, the Video Electronics Standards Association (VESA) agreed on a standard implementation of SVGA that provided up to 16.8 million colors and 1280x1024 resolution. Most graphics cards available today support Ultra Extended Graphics Array (UXGA). UXGA can support a palette of up to 16.8 million colors and resolutions up to 1600x1200 pixels.

          Even though any card you can buy today will offer higher colors and resolution than the basic VGA specification, VGA mode is the de facto standard for graphics and is the minimum on all cards. In addition to including VGA, a graphics card must be able to connect to your computer. While there are still a number of graphics cards that plug into an Industry Standard Architecture (ISA) or Peripheral Component Interconnect (PCI) slot, most current graphics cards use the Accelerated Graphics Port (AGP).

Peripheral Component Interconnect(PCI)

          There are a lot of incredibly complex components in a computer. And all of these parts need to communicate with each other in a fast and efficient manner. Essentially, a bus is the channel or path between the components in a computer. During the early 1990s, Intel introduced a new bus standard for consideration, the Peripheral Component Interconnect (PCI).It provides direct access to system memory for connected devices, but uses a bridge to connect to the front side bus and therefore to the CPU.

          The illustration above shows how the various buses connect to the CPU.

          PCI can connect  up to five external components. Each of the five connectors for an external component can be replaced with two fixed devices on the motherboard. The PCI bridge chip regulates the speed of the PCI bus independently of the CPU's speed. This provides a higher degree of reliability and ensures that PCI-hardware manufacturers know exactly what to design for.

          PCI originally operated at 33 MHz using a 32-bit-wide path. Revisions to the standard include increasing the speed from 33 MHz to 66 MHz and doubling the bit count to 64. Currently, PCI-X provides for 64-bit transfers at a speed of 133 MHz for an amazing 1-GBps (gigabyte per second) transfer rate!

          PCI cards use 47 pins to connect (49 pins for a mastering card, which can control the PCI bus without CPU intervention). The PCI bus is able to work with so few pins because of hardware multiplexing, which means that the device sends more than one signal over a single pin. Also, PCI supports devices that use either 5 volts or 3.3 volts. PCI slots are the best choice for network interface cards (NIC), 2-D video cards, and other high-bandwidth devices. On some PCs, PCI has completely superseded the old ISA expansion slots.

         

          Although Intel proposed the PCI standard in 1991, it did not achieve popularity until the arrival of Windows 95 (in 1995). This sudden interest in PCI was due to the fact that Windows 95 supported a feature called  Plug and Play (PnP). PnP means that you can connect a device or insert a card into your computer and it is automatically recognized and configured to work in your system. Intel created the PnP standard and incorporated it into the design for PCI. But it wasn't until several years later that a mainstream operating system, Windows 95, provided system-level support for PnP. The introduction of PnP accelerated the demand for computers with PCI.

Accelerated Graphics Port (AGP)

          The need for streaming video and real-time-rendered 3-D games requires an even faster throughput than that provided by PCI. In 1996, Intel debuted the Accelerated Graphics Port (AGP), a modification of the PCI bus designed specifically to facilitate the use of streaming video and high-performance graphics.

          AGP is a high-performance interconnect between the core-logic chipset and the graphics controller for enhanced graphics performance for 3D applications. AGP relieves the graphics bottleneck by adding a dedicated high-speed interface directly between the chipset and the graphics controller as shown below.

Conclusion

             From the introduction of the first 3D accelerator from 3dfx in 1996 these units have come a long way to be truly called a “Graphics Processing Unit”. So it is not a wonder that this piece of hardware is often referred to as an exotic product as far as computer peripherals are concerned. By observing the current pace at which work is going on in developing GPUs we can surely come to a conclusion that we will be able to see better and faster GPUs in the near future.