The Graphics Card - APIs, Chipsets, and Cards

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In choosing a graphics card, you’ll be faced with a dictionary’s worth of mumbo jumbo that we’ll help you understand. Based on the e-mail that this author receives, the most confusing aspects of the decision process is figuring out the difference between 3-D APIs, 3-D chipsets, and graphics cards themselves.

3-D APIs

API stands for application programming interface. At its most basic, it’s a software layer that makes hardware, software, and the operating system compatible with one another. An API provides programmers with a set of common, compatible instructions so that they don’t have to bother with programming to specific cards and chipsets; as long as they program to an API, they theoretically don’t have to deal with the rigors of making their software compatible with all the hardware that’s available, or with the operating system itself.

For example, if a programmer writes to a 3-D hardware API such as Microsoft’s Direct3D, he shouldn’t have to worry about his program’s compatibility with all of the different Direct3D-compliant graphics cards that are available. Similarly, if a graphics card manufacturer builds its hardware with Direct3D-com-patible parts and drivers, it shouldn’t have to worry about compatibility with Direct3D-compliant programs. An API smoothes the way for both sides.

It would be terrific if that theory held up in practice, but incompatibilities creep up in even the best laid programs. Good game companies put their wares through countless hours of compatibility testing on the vast majority of computer hardware in circulation. Even so, games are often released with incompatibilities that the programmers didn’t know about when the game shipped. These are usually addressed in patches, which are downloadable updates to their products.

Two major 3-D APIs are in use today: OpenGL and Direct3D.

OpenGL

Developed by Silicon Graphics, Inc., OpenGL is widely used by 3-D modelers for high-end business applications. When John Carmac optioned to use OpenGL for the first 3-D accelerated version of Quake (commonly called GLQuake), OpenGL was embraced by the gaming community and is used by many game developers today. The current version of OpenGL is version 1.3.

Direct3D/DirectX

Part of Microsoft’s DirectX library of APIs, Direct3D is more popular among game developers for 3-D programming—but getting there took a while. Early versions of DirectX were widely considered incomplete and difficult to program to. By the time DirectX 5 came out, Direct3D had evolved into a feature-rich, pro-grammer-friendly API, and with each incarnation of DirectX it’s gotten better.

Both OpenGL 1.3 and DirectX 8.1 are supported by virtually every graphics card available on the market today, so you don’t have to worry about checking for compatibility before you purchase a card. The latest version of Direct3D, part of DirectX 9’s library, is supported by only the very latest graphics hardware.

Chipsets

Like motherboards, all graphics cards are based on one or another chipset. The chipset incorporates the logic on the graphics card, including the graphics processing unit (GPU), which does the grunt work of creating 3-D graphics. The chipset determines such factors as the APIs with which the card is compatible, how much video memory it supports, its Accelerated Graphics Port (AGP) support, and the clock frequencies of the core logic and the memory.

Companies such as ATI, Nvidia, and SiS create graphics chipsets and license them to final market card manufacturers. Nvidia and SiS don’t market cards to the public; they only create chipsets. Another manufacturer, Matrox, makes its own chipsets and cards. ATI makes chipsets and cards, and it also licenses its chipsets to other manufacturers to make cards. It’s a bit confusing; Table 3-1 should help.

Manufacturer	Makes Chipsets	on Its Chipsets	Chipsets
ATI	Yes	Yes	Yes
Matrox	Yes	Yes	No
Nvidia	Yes	No	Yes
SiS	Yes	No	Yes

Table 3-1 Chipsets Makers’ Roles in the Graphics Card Industry

Cards

Graphics cards themselves are made by a huge variety of manufacturers. The players include ATI, Matrox, ASUS, Crucial, Gigabyte, MSI, Leadtek, PNY, and ABIT.

Card manufacturers license chipsets from chipset manufacturers (except in the case of ATI and Matrox, who make their own chipsets). Cards are produced based on a particular chipset. Some card manufacturers stick very close to the reference design, or the sample cards created by the chipset manufacturers, while others take liberties with their drivers’ capabilities or the configurations of their cards. For the most part, though, the chipset determines the speed and feature set of the card. For instance, a PNY card based on the Nvidia GeForce4 Ti 4600 chipset performs almost identically to an ABIT card based on the same chipset.

The major differences between cards based on the same chipset isn’t performance—it’s the price, availability, and warranty offered by the card manufacturer. The price range is determined by a chipset (for instance, the GeForce Ti 4600 is available on cards ranging from $200 to $300), but the card manufacturer determines any variance within that range. Usually, you’ll want to decide on a chipset first, and then you can check to see what card manufacturers have to offer with your chosen chipset.

This chapter is from Build Your Own High Performance Gamers' Mod PC, by Chen and Durham (McGraw-Hill/Osborne, 2004, ISBN: 0072229012). Check it out at your favorite bookstore today. Buy this book now.

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