ATI CrossFire - Multi-GPU Rendering Preview - PAGE 1

Introduction

Utilizing multiple video cards to increase performance is not a new concept. On the consumer graphics side, the first implementation was seen with 3dfx's Voodoo 2 SLI. The Voodoo 2 had great success because the single card was a performance leader and the addition of a second Voodoo 2 meant that performance leapfrogged that of all other solutions on the market at the time. The second company to harness the power of a second video card is none other than ATI with their RAGE MAXX which featured a pair of RAGE 128 Pro processors on a single card. While it was a technological curiosity, the name of the game in those days was hardware T&L pushed heavily by a familiar graphics giant and the RAGE MAXX became lost in the shuffle. 3dfx doggedly pursued the dual video processor path with the Voodoo 5 5500, but ultimately it also fell short on the performance front. Beyond the Voodoo 2, the failure of multi video processor implementations back then was not because it was not interesting, it was the fact that the single core implementations of the successive GPUs were not competitive and multi-card rendering was used as a crutch to play catch up.

Today, the graphics landscape has changed somewhat. ATI and NVIDIA both have compelling products at the high end of the market and neither company is using multi-video card technology to catch up to a single card from the competitor. In single card solutions, NVIDIA and ATI basically split most benchmark suites as both cards have their strong suits in different games, Half-Life 2 and DOOM 3 being two of the obvious contrasts. The difference however is multi-card rendering and NVIDIA has had the benefit of their implementation, SLI, on the market for over six months now. In many cases SLI offers a significant performance improvement over single card solutions and ATI has had no answer until now, with the introduction of their Crossfire technology.

CrossFire

CrossFire refers to all the components that make up ATI's multi-GPU rendering solution. Those who already own a X800 or a X850 PCIe based video card already have the first component of a CrossFire solution. The second component is a CATALYST driver that supports CrossFire. The last two components unfortunately, do cost money and they are the following -

• A RADEON CrossFire Edition Graphics Card with Compositing Engine
• CrossFire certified motherboard

ATI has a different approach with the second video card. Unlike the NVIDIA solution which is built onto the NV4x silicon, ATI relies on an external chip dubbed the Compositing Engine which blends the final image together. ATI's implementation of CrossFire is fairly unique and arguably affords the end user more flexibility when upgrading compared to NVIDIA's SLI. As mentioned previously, current owners of ATI X800 and X850 PCIe cards have the first CrossFire component already. The second component required is the second video adapter and here is where ATI should have an advantage. There are only three CrossFire Edition cards and they are the following:

Do note that there are many more than three permutations of X850 and X800s on the market. The X850 Crossfire will work with any X850 class card and unsurprisingly, the X800 will pair up with X800 cards. There are a couple caveats to bring up however. ATI claims that differences in clock speed will not result in the two cards scaling to the lowest clock speed