Monday, October 26th 2015

DirectX 12 Mixed Multi-GPU: It Works, For Now

One of biggest features of DirectX 12 is its asymmetric multi-GPU that lets you mix and match GPUs from across brands, as long as they support a consistent feature-level (Direct3D 12_0, in case of "Ashes of the Singularity"). It's not enough that you have two DirectX 12 GPUs, you need DirectX 12 applications to make use of your contraption. Don't expect your older DirectX 11 games to run faster with a DirectX 12 mixed multi-GPU. Anandtech put Microsoft's claims to the test by building a multi-GPU setup using a Radeon R9 Fury X, and a GeForce GTX 980 Ti. Some interesting conclusions were drawn.

To begin with, yes, alternate-frame rendering, the most common multi-GPU method, works. There were genuine >50% performance uplifts, but nowhere of the kind you could expect from proprietary multi-GPU configurations such as SLI or CrossFire. Second, what card you use as the primary card, impacts performance. Anandtech found a configuration in which the R9 Fury X was primary (i.e. the display plugged to it), and the GTX 980 Ti secondary, to be slightly faster than a configuration in which the GTX 980 Ti was the primary card. Mixing and matching different GPUs from the same vendor (eg: a GTX 980 Ti and a GTX TITAN X) also works. The best part? Anandtech found no stability issues in mix-matching an R9 Fury X and a GTX 980 Ti. It also remains to be seen how long this industry-standard utopia lasts, and whether GPU vendors find it at odds with their commercial interests. Multi-GPU optimization is something both AMD and NVIDIA spend a lot of resources on. It remains to be seen how much of those resources they'll be willing to put on a standardized multi-GPU tech, and away from their own SLI/CrossFire fiefdoms. Read the insightful article from the source link below.
Source: AnandTech
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55 Comments on DirectX 12 Mixed Multi-GPU: It Works, For Now

#51
deemon
FordGT90Concept, post: 3364001, member: 60463"
I think PhsyX hardware acceleration is disabled in the presence of an AMD card. I suspect NVIDIA did the same to HairWorks. FreeSync would require the AMD to be primary. It might work because the primary card has to always transmit the completed frames to the monitor in a language it understands.
One would assume that PhysX is enabled in the presence of NVIDIA card, not disabled when AMD is also detected... same thing with hairworks.
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#52
hariszhr
matar, post: 3362330, member: 96547"
This is the best games news since DX9 now you can put your old cards to use, excellent Microsoft and now that windows 10 is free no one can complain that DX12 is only for windows 10 only.
Depends on how old your GPUs are. If they dont support DX12, they are still pretty much useless.
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#53
HossHuge
So a bridge is no longer needed?
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#54
hariszhr
HossHuge, post: 3386123, member: 55273"
So a bridge is no longer needed?
if u use the bridge u will be using amd drivers for dual Gpu performance. If u dont use bridge then u would be using dx12 to use dual gpu. I would say, stick with the bridge for now. I dunno how many games benefit from dx12 multi gpu feature.
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#55
Xzibit
HossHuge, post: 3386123, member: 55273"
So a bridge is no longer needed?
hariszhr, post: 3386139, member: 161640"
if u use the bridge u will be using amd drivers for dual Gpu performance. If u dont use bridge then u would be using dx12 to use dual gpu. I would say, stick with the bridge for now. I dunno how many games benefit from dx12 multi gpu feature.
I believe he is referring to Nvidia cards. When paired with a AMD GPU since most AMD cards don't have bridge fingers now.

DX12 dual-GPU is software based through App/Game that's why your able to pair a Nvidia which needs a bridge to a AMD which doesn't use bridges together.
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