Video FAQs

Q: What is graphics accelerator?

A:A type of video adapter that contains its own processor to boost performance levels. These processors are specialized for computing graphical transformations, so they achieve better results than the general-purpose CPU used by the computer. In addition, they free up the computer’s CPU to execute other commands while the graphics accelerator is handling graphics computations.
The popularity of graphical applications, and especially multimedia applications, has made graphics accelerators not only a common enhancement, but a necessity. Most computer manufacturers now bundle a graphics accelerator with their mid-range and high-end systems.

Aside from the graphics processor used, the other characteristics that differentiate graphics accelerators are:

memory : Graphics accelerators have their own memory, which is reserved for storing graphical representations. The amount of memory determines how much resolution and how many colors can be displayed. Some accelerators use conventional DRAM, but others use a special type of video RAM (VRAM), which enables both the video circuitry and the processor to simultaneously access the memory.
bus : Each graphics accelerator is designed for a particular type of video bus. As of 1995, most are designed for the PCI bus.
register width: The wider the register, the more data the processor can manipulate with each instruction. 64-bit accelerators are already becoming common, and we can expect 128-bit accelerators in the near future.

Q: What is AGP?

A: Short for Accelerated Graphics Port, an interface specification developed by Intel Corporation. AGP is based on PCI, but is designed especially for the throughput demands of 3-D graphics. Rather than using the PCI bus for graphics data, AGP introduces a dedicated point-to-point channel so that the graphics controller can directly access main memory. The AGP channel is 32 bits wide and runs at 66 MHz. This translates into a total bandwidth of 266 MBps, as opposed to the PCI bandwidth of 133 MBps. AGP also supports two optional faster modes, with throughputs of 533 MBps and 1.07 GBps. In addition, AGP allows 3-D textures to be stored in main memory rather than video memory.

AGP has a couple important system requirements:
-The chipset must support AGP.
-The motherboard must be equipped with an AGP bus slot or must have an integrated AGP graphics system.
-The operating system must be the OSR 2.1 version of Windows 95, Windows 98 or Windows NT 4.0. And currently, many professional Macintoshes support AGP.

AGP-enabled computers and graphics accelerators hit the market in August, 1997. However, there are several different levels of AGP compliance. The following features are considered optional:

Texturing: Also called Direct Memory Execute mode, allows textures to be stored in main memory.
Throughput: Various levels of throughput are offered: 1X is 266 MBps, 2X is 533 MBps; and 4X provides 1.07 GBps.
Sideband Addressing: Speeds up data transfers by sending command instructions in a separate, parallel channel.
Pipelining: Enables the graphics card to send several instructions together instead of sending one at a time.

Q: What is SGRAM?

A:Abbreviation of Synchronous Graphic Random Access Memory, a type of DRAM used increasingly on video adapters and graphics accelerators. Like SDRAM, SGRAM can synchronize itself with the CPU bus clock up to speeds of 100 MHz. In addition, SGRAM uses several other techniques, such as masked writes and block writes, to increase bandwidth for graphics-intensive functions.
Unlike VRAM and WRAM, SGRAM is single-ported. However, it can open two memory pages at once, which simulates the dual-port nature of other video RAM technologies.

Q: What is 3-D graphics?

A: The field of computer graphics concerned with generating and displaying three-dimensional objects in a two-dimensional space (e.g., the display screen). Whereas pixels in a 2-dimensional graphic have the properties of position, color, and brightness, a 3-D pixels adds a depth property that indicates where the point lies on an imaginary Z-axis. When many 3-D pixels are combined, each with its own depth value, the result is a three-dimensional surface, called a texture. In addition to textures, 3-D graphics also supports multiple objects interacting with one another. For example, a solid object may partially hide an object behind it. Finally, sophisticated 3-D graphics use techniques such as ray tracing to apply realistic shadows to an image.

Converting information about 3-D objects into a bit map that can be displayed is known as rendering, and requires considerable memory and processing power. In the past, 3-D graphics was available only on powerful workstations, but now 3-D graphics accelerator are commonly found in personal computer. The graphics accelerator contains memory and a specialized microprocessor to handle many of the 3-D rendering operations.