Triple-GPU Scaling: AMD CrossFire Vs. Nvidia SLI

Is Multi-GPU The Game Changer?

Tom's Hardware's Three-Part, 3-Way Graphics Scaling Series

Part 1, The Cards: Triple-GPU Scaling: AMD CrossFire Vs. Nvidia SLI
Part 2, The Slots: GeForce And Radeon On Intel's P67: PCIe Scaling Explored
Part 3, The Chipsets: P67, X58, And NF200: The Best For CrossFire And SLI

The battle for GPU supremacy is a bit of a waiting game. The recent launch of AMD's Radeon HD 6990 (AMD Radeon HD 6990 4 GB Review: Antilles Makes [Too Much] Noise) and upcoming introduction of Nvidia's GeForce GTX 590 help demonstrate.

Roughly every six moths, two companies with similarly-capable products wait to see what the other one will showcase, hoping to trump that introduction a few days later by tweaking the clocks, power, and configuration of their own product. Both firms use these delays to build anticipation among followers. Though, as that very same 6990 story showed us, being a "fan" of either company is just silly. Why make excuses for one design team's poor execution and then slam the competition for the very same thing? 

Yet, in spite of the hysteria, the past few GPU launches have barely budged the performance bar. For those who prefer to play at high resolutions without giving up any of a modern game’s splendor, multi-GPU configurations (and that includes the latest and upcoming dual-GPU cards) are still mandatory.

Launch articles rarely include multi-GPU tests, partly because most reviewers have only one card. The few reviewers that do get multiple cards often find SLI and CrossFire bugs persisting until two or three software revisions after a new card is launched, leading to hopeful comments from loyal enthusiasts like, "just wait until they get their driver situation worked out!"

As a result, when we as reviewers get asked about multi-GPU scaling, it's often really hard to answer definitively. The real data has to be collected once availability is more stable, and after driver problems have been more thoroughly addressed. 

It's Time To Explore Multi-Card Scaling

Today’s question isn’t which single-GPU card is best, but which cards operate best in pairs and trios. Though current buyers can now save even more money with the 1 GB version, AMD's Radeon HD 6950 2 GB was its least expensive three-way CrossFire option when we set up this article.

The closest competitor is Nvidia’s GeForce GTX 570 1280 MB, a model that also represents its cheapest-current three-way SLI configuration. Anything less and you only get a single SLI link, support two-way setups.

We've already seen fantastic scaling from three-way SLI, so perhaps the biggest question is whether AMD’s scaling had really improved to the point where it can yank the trophy out of its rival’s hands. We've seen two-way numbers that suggest yes, in fact, Radeons work much better together now than in the past.