Graphics Cards: The Other Processing Unit
Maybe you need to upgrade your workstation PCs at your small business because you are taking on more 3D development. Maybe your kids want the latest games but alas, your home computer can’t handle the graphics load. Whatever reason you have for shopping for a graphics card, the terms, choices, and brand variety out there can be daunting. We’ve assembled this helpful guide to what graphics cards are and how they operate in order to better prepare you for your purchase! After reading this, you can converse knowledgably with the tech guys without feeling out of the loop. Good Luck!
An Introduction To Graphics Cards
Any image displayed on a monitor is made up of thousands of pixels. Most common resolution settings display over a million pixels at once. The computer has to decide what to do with them all in order to properly display an image. It needs a translator to do this. A “translator” in this case, is a device that takes binary data from the processor and turns it into an image. That translation takes place on the graphics card, unless the computer’s motherboard has graphics capability built in.
A Graphics processor has a very complex job to do. Luckily, its principle components and functions aren’t difficult to understand. In this article, we’ll try and explain the basic parts of a video card, as well as what they do. We’ll also tell you what factors work together to make fast, efficient graphics cards.
Graphics Processors: The Basics
The graphics processor of a PC is essentially a dedicated video production center within the computer. It is responsible for properly assembling a desired image or graphic (like what happens on the screen in a video game) and for displaying it correctly on the monitor screen. The end result is that indecipherable lines of code eventually become an actual, viewable picture.
A graphics card works along much of the same principles as the computers Central Processing Unit, or CPU. The CPU works in conjunction with software applications to send information about the image to the graphics processor. The graphics card determines how to use the pixels on the screen to create an image. It then conveys that information to the monitor.
Building images out of binary data is a demanding process. To make a 3-D image, the graphics card first creates a “frame” out of straight lines, much like an architectural drawing. It then rasterizes the image (rasterizing means filling in the remaining pixels). It also adds lighting, texture and color effects. For fast-paced games, the computer repeats this process at least sixty times per second. Without a graphics card to perform these calculations, the workload would be too much for consumer computers to handle.
The graphics card accomplishes the task of building graphics and images using the following components. We will outline the general uses and important roles of these parts of the graphics card.
-A connection to the motherboard that feeds data and electricity to the GPU.
Graphics cards connect to the computer through the motherboard. The motherboard supplies power to the card and allows communication with the central processor. Newer graphics cards often require more power than the motherboard can provide, so they may also be directly connected to the computer’s power supply.
Connections to the motherboard are usually through one of three interfaces:
1. Peripheral component interconnect (PCI)
2. Advanced graphics port (AGP)
3. PCI Express (PCIe)
It is important to note that PCI Express is the newest of the three and provides the fastest transfer rates between the graphics card and the motherboard. PCIe also supports the use of two graphics cards in the same computer.
-A processor that determines the correct use for each pixel.
A graphics card has an input/output system (BIOS) chip, which stores setting information and performs diagnostics on the memory, input and output at when the GPU is started up. A graphics card is a printed circuit board that houses a processor and RAM, just like a motherboard does. The difference is that a GPU is designed specifically for performing the complex mathematical and geometric calculations necessary for rendering graphics. Some of the fastest GPUs can have more transistors than the average CPU. Because of this, a GPU produces a lot of heat. Most graphics cards are equipped with a dedicated heat sink or fan.
In addition to its processing capacity, a GPU uses special programs to help it analyze and interpret data.
There are two techniques that graphic processors use to improve image quality:
Full scene anti aliasing (FSAA)- This smoothes the edges of 3-D objects.
Anisotropic filtering (AF)-This makes images appear crisper.
Graphics card manufacturers have developed additional brand specific techniques that assist the GPU when applying shades, textures and colors to an image.
-Memory to hold image and pixel information, as well a temporary cache for completed pictures.
As the GPU assembles image information, it needs somewhere to hold that information, as well as completed pictures. The graphics card uses Random Access Memory, (or RAM) for this purpose. It uses RAM to store data about each pixel: specifically its color as well as its location on the screen. Part of the RAM can also act as a frame buffer, which means that it holds completed images until it is time to display them. Video RAM operates at high speeds and is typically dual-ported, which means that the system can read from and write to the video card’s memory at the same time. The RAM connects directly to the digital-to-analog converter. This converter is called the DAC for short, and is sometimes called the RAMDAC. The DAC translates the image into an analog signal to be sent to the computer monitor. Some cards have multiple DACs, in order to support more than one monitor. This also improves performance for a single monitor configuration. The DAC sends the final picture to the monitor through a cable.
-A Monitor interface that connects the GPU directly to the monitor, in order to display finished graphics information.
Most graphics cards have two monitor connections. Often, one is a DVI connector, which supports LCD screens, and the other is a VGA connector, which supports CRT screens. Some graphics cards have two DVI connectors instead. But that doesn’t rule out using a CRT screen; CRT screens are connectible to DVI ports via an adapter.
Most people use only one of their two possible monitor connections. People who need to use two monitors can purchase a graphics card with dual head capability, which splits the display between the two screens. Theoretically, computer with two dual head, PCIe-enabled video can theoretically support four monitors.
In addition to connections for the motherboard and monitor, some graphics cards have connections for:
· TV display: TV-out or S-video
· Analog video cameras: ViVo or video in/video out
· Digital cameras: FireWire or USB
· Some cards can also incorporate TV tuners.
How Do I Choose The Graphics Card That’s Right For Me?
A top-of-the-line graphics card has lots of memory and a fast processor. It’s also more visually appealing than anything else that’s intended to go inside a computer. Lots of high-performance video cards are illustrated or have decorations adorning fans or heat sink mechanisms.
But a high-end card provides more graphics processing power than most people need. Those who use their computers primarily for e-mail, word processing or Web surfing can have all the necessary graphics support by using a motherboard with integrated graphics, and mid-range cards are sufficient for most casual gamers. Gaming enthusiasts and people who do lots of 3-D graphic work will require the power of high-end graphics cards.
A good overall measurement of a card’s performance is its frame rate, which is measured in frames per second (FPS). The frame rate describes how many complete images the card can generate and display per second. The human eye can process about 25 frames every second. Fast-action games require a frame rate of at least 60 FPS to provide smooth animation and scrolling. Frame rates are broken down into separate components:
Triangles (or vertices) per second: 3-D images are made of triangles, or polygons. This measurement describes how quickly the GPU can calculate the whole polygon or the vertices that define it. In general, it describes how quickly the card builds a wire frame image.
Pixel fill rate: This measurement describes how many pixels the GPU can process in a second, which translates to how quickly it can rasterize the image.
The graphics card’s hardware directly affects its speed. These are the hardware specifications that matter most:
· GPU clock speed (MHz)
· Size of the memory bus (bits)
· Amount of available memory (MB)
· Memory clock rate (MHz)
· Memory bandwidth (GB/s)
· RAMDAC speed (MHz)
The computer’s CPU and motherboard also play a part, since a very fast graphics card can’t compensate for a motherboard’s ability (or lack thereof) to deliver data quickly. The card’s connection to the motherboard and the speed at which it can get instructions from the CPU can affect performance as well.
Whether you’re stepping up your 3D rendering at work or home or outfitting your machine for gaming, graphics cards are an important part of your PC. We hope this brief introduction to graphics cards has helped you determine what’s out there, what these many options mean, and finally which graphics card is right for you!
Leave a Reply