Leaping Beyond Two Screens
There are different ways to create a multi-monitor surface. Nvidia drew some eyeballs at CES 2010 with the demonstration of its 3D Vision Surround technology, but this approach required two boards, controlled and synchronized with software. Each card could still only output to two displays, as they’ve done for years. There was no increase in hardware-based surface scalability. The implementation still required two cards, an SLI-capable motherboard to run them, and more overall power compared to a single-card solution.
With Eyefinity, one card can drive up to six displays (depending on the model, of course). AMD states that all 5000-series GPUs support Eyefinity. However, it falls to the graphics card manufacturer to decide whether and how Eyefinity will be implemented on a given card. As of this writing, only the 5800 models have Eyefinity enabled in CrossFire mode, and it seems reasonable to expect that bandwidth plays a part in this decision. With the Radeon HD 5970 freshly placing AMD back in the lead for desktop GPU performance, the last thing AMD wants to risk is a bunch of 5400-series buyers trying to span Left 4 Dead 2 across three screens at maximum settings and wondering what why it isn’t playable. Having the display connectivity for multiple displays is one thing, but putting the muscle behind those pipelines is something else, and vendors need to pair their output paths and GPUs appropriately.
Just to be clear, the Radeon HD 4000-series GPUs and all of their predecessors do not support Eyefinity. The GPUs, good as they were, don’t have the horsepower or display output connectivity needed to fuel more than two high-resolution displays.
“For 2D applications, like for productivity work, the bandwidth load is no problem at all,” says Shane Parfitt, product manager in AMD’s GPU division. “Where you get into performance situations is 3D games with 3x the number of pixels in a 3x1 configuration. That’s definitely harder on the GPU. Our GPUs right now are the most powerful on the planet. We test with 30" panels—the 2560x1600 panels with over 6 million pixels each. Sometimes, you might have to turn down the anti-aliasing settings in order for a game to run at at least 30 fps. An average case of 19x12 running across three panels, we find, performs pretty well, especially with the higher-end cards.”
What about harnessing two or more GPUs to buy more multi-display bandwidth?
“We’re just now rolling CrossFire support out,” says Parfitt. “We had a lot of demand from the market for this feature, so we rolled it out in a hotfix driver. But it became an official feature in the February Catalyst release.”
Specifically, in November, the Radeon HD 5970 became the first GPU to support Eyefinity with CrossFire at a time when only 20 or so applications had been validated for CF/Eyefinity compatibility. Only three months later, the feature was enabled across the board. It deserves mention that making this happened required massive testing and troubleshooting effort on AMD’s part, and its driver crew should get bonus kudos for their beyond the call of duty labors.