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AMD will fix CrossFireX ‘runt’ frame issues at end of July

by Mark Tyson on 24 June 2013, 10:45


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AMD has tweeted advanced notice of its plans to release an updated driver to improve the performance of its Radeon graphics cards in CrossFireX configuration. The new driver, due on 31st July should it be on schedule, will implement “improved multi-GPU frame pacing” in the AMD Catalyst software, to eliminate such issues as micro-stutter.

Users running two AMD graphics cards (or a graphics card and an APU) have been suffering from some performance issues; the reported frame rates suggested smooth performance but users often experienced something else; stuttering. Apparently AMD CrossFireX solutions were rendering a large number of ‘runt’ frames which counted towards the reported frame rates but were never used to provide smooth gameplay action on screen.

CrossFireX should, in-theory, provide a significant boost to a user’s gaming frame rates. It is an attractive selling point for AMD’s APU’s, for example, when you can buy a relatively cheap graphics card and receive a big boost in 3D power. In our look at an AMD A10-5800K APU paired with a discrete Radeon HD 6670 we found that frame rate measurements could be up to 40 per cent better, like in Dirt Showdown, or practically non-existent, as in Batman: Arkham City. However even high end CrossFireX pairings suffered from micro-stuttering.

AMD promised a fix for these CrossFireX issues alongside the unveiling of the HD7990 earlier in the year. Nvidia had similar stuttering problems with its SLI configurations before its Kepler GPU introduction. “Frame pacing” is also the technique which Nvidia used to fix this issue.

HEXUS Forums :: 17 Comments

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Well let's hope this matches the timings from the game engines.
In a general level, I suspect that this is entirely due to the Crossfire method of rendering, i.e., Alternate Frame Rendering.

Old school techniques like SLI, and even splitting up a single frame into two (or three) portions for two (or three) graphics cards would not need pacing, as they'd always be rendering the same frame together.

Obviously there are drawbacks to that method, hence the use of AFR today. What are they? I know that the exact same frame geometry would need sending to both GPUs, which is a hassle, but it's not like PCIe is slow. And both GPUs need the textures cached anyway. Any ideas from those more in the know?
Doesn't SLI do that too? Despite the name.
14yrs after having a pair of Voodoo 2 cards in Sli (for a mind bending 1024x768 resolution in Unreal) I can't believe that dual card set-ups are still suffering from issues like this…
Still, better than them not even attempting to address the issue, so for me, I'm happy that they have put time and effort into it. Let see how they get on. For their sake, I hope they get it right, otherwise people are going to rip into them.