Dual Graphics Cards

For users who want the fastest, most versatile, and highest possible graphics performance from their computer system, there are many available options for installing multiple graphics cards. With double the video memory and two Graphics Processing Units (GPUs) instead of one, computer systems with dual graphics cards - provided the graphics cards are relatively new - typically are able to run 3D software and games at maximum settings.

Systems with dual graphics cards - also known as multi-GPU systems - will provide superior:

And more. Essentially, computers with two graphics cards are able to run 3D applications with everything turned on. Unlike most single-card computers, multi-GPU systems are not forced to choose between detail and performance.

Why Use Two Graphics Cards?

There is only one answer to this question: performance! Purchasing two graphics cards isn't cheap, but the increase in graphics output is stunning.

Adding a second GPU not only doubles overall image processing capability, it allows the GPU to manage new and exciting technologies like physics engines and motion blur effects, creating a more compelling and immersive graphical world.

Since resolutions on most modern monitors are fixed at 1920 x 1080 for widescreen displays and 1280x1024 for full screen displays, the additional power of the second card can be used almost exclusively to add flavor and pizzazz to the game environment.

If the goal is eye-candy, a multi-GPU system is the way to go.

Dual Card Setups

For users that want to use more than one graphics card, there are presently two name-brand options: Scaled Link Interface (SLI) and CrossFireX.

SLI

Developed by graphics giant Nvidia in 2004, SLI is a proprietary technology that allows the linking of two identical Nvidia graphics cards to produce composite images.

In an SLI setup, two Nvidia cards are linked together by a small connector, with one card designated the "master" and the second card designated the "slave." The master graphics card acts as the main access point to the monitor, and the graphics workload is shared evenly between the two cards.

SLI is generally transparent, meaning the user simply needs to install the appropriate hardware and activate SLI mode from the Nvidia control panel. Once active, the Nvidia software automatically performs the workload sharing. Depending on the application, SLI will use one of several different modes of load sharing to achieve optimal performance.

CrossFireX

Developed initially by ATI Technologies in 2004, the original CrossFire dual-card setup has been improved, and was re-released in 2007 as CrossFireX. ATI was bought out by Advanced Micro Devices (AMD) in 2006, and CrossFireX is now marketed under the AMD logo.

CrossFireX is similar to SLI in that the management of work sharing is transparent to the user. Once activated, CrossFireX software automatically determines the best method of sharing graphics processing between the attached graphics cards.

CrossFireX differs from SLI in that it does not require two identical graphics cards, but allows a broad range of Radeon series graphics cards to be linked in a CrossFireX configuration.

More Than Two Graphics Cards

Both SLI and CrossFireX support even more than two graphics cards, for computer users who are extremely serious about performance.

Provided the computer can handle it, SLI and CrossFireX can be configured to use up to four graphics cards in a single array. While this much horsepower is well beyond the requirements of nearly any 3D software or application presently available, quad-card systems are sometimes implemented in industrial or business workstations that use high-end designing or engineering software.

For gamers, quad-card systems border on overkill. A dual-card system utilizing two relatively modern graphics cards will handle nearly any game on the market, at full resolution and detail, while maintaining excellent frame rates.

The only gamers who might implement a quad-card system are those who are not planning on upgrading for a long time, or those who have a pile of older graphics cards that may not be able to perform at maximum settings with only two cards linked.

Cost, Heat, and Power!

There are several reasons that not every computer houses two graphics cards.

Cost

Chief among these reasons is cost. Modern graphics cards range in cost from $100 for a bare-bones card, to $700 for a top-of-the-line monster. Typically, users who opt for dual graphics cards will want to spend a minimum of $300 on a solid card - perhaps a bit more.

Dual graphics card setups also require a specific type of motherboard that supports multiple GPUs, as the proprietary technology that enables either SLI or CrossFireX configurations must be purchased as well.

All said and done, dual card systems will require the user to fork out an extra $400-$800. Quality comes at a cost.

Heat

Graphics cards generate a tremendous amount of heat inside the computer. By installing a second card, that heat generation spikes dramatically, and some form of reliable heat management system needs to be implemented to keep the computer stable.

Liquid cooling systems are available for most computers, providing an excellent way to keep temperatures down. However, these systems are also costly, and come with their own range of limitations.

Power

Modern graphics card suck up electricity at an alarming rate. Mid- to high-end graphics cards will pull as many as 300 Watts of power, which is roughly equivalent to running two full-sized refrigerators, per graphics card.

This power consumption means not only a larger power bill at the end of the month - yet another cost - but also requires the use of a specialized Power Supply Unit (PSU) that can provide enough juice to keep the system running.

Dual Graphics Card Summary

Dual graphics cards provide unparalleled performance, speed, and detail in all forms of graphic-intensive applications. However, multi-GPU systems are not cheap, and require specialized components to keep everything running smoothly.

For users seeking the ultimate gaming experience, dual cards are worth the expense. For casual users, multiple cards probably isn't worth the time and trouble.