While much of the talk around DX12 recently has been around the reduced CPU/driver overhead and AsyncCompute, another feature is getting its first real world test. Dubbed Explicit Multi-Adapter in Microsoft’s material, the feature allows multiple GPUs that support DX12, irrespective of vendor, to work together on the same task. Developer Oxide has created a Multi-Adapter demo from their now famous Ashes of the Singularity title, using the in-house Nitrous engine.
While DX12 continues to allow the GPU drivers to allow multi-GPU setups like SLI and Crossfire, Microsoft has decided to build in a more powerful feature right into DX12. This means if the developer takes the time and effort to implement it, any DX12 title will allow any 2 DX12 card work together and boost performance. This is exactly what Anandtech tested when Oxide provided a custom build of Ashes of the Singularity with early support.
Using the built-in DX12 Multi-Adapter, top end cards like the Fury X, 980Ti and Titan X were able to show gains of between 46 to 72%. While lower than what Crossfire can offer at about 80% gains, this is pretty crazy considering the fact that it is using two cards with vastly different architectures at times from 2 different vendors. Interestingly enough, combinations with the Fury X as primary card out did those with the Nvidia card as the main one, even when the Titan X was used. This held true of older cards like the 7970 vs the 680, with the 680+7970 doing worse than just the 680 or 7970 alone. This may be due to the inherent nature of AMD’s GCN architecture being better suited to the task, but it’s still early in the game.
If developers choose to make use of this feature later on, it could make big performance boosts in teh future. Instead of having to buy two of a card, gamers can just use 1 higher performance card with a lower end one. When it comes time to upgrade, the weaker card can be tossed out and a new top-tier card takes control of the old master card. This extends to pairing up mostly unused iGPUs to get that extra bit of eye candy and fps. With control in the hands of developers and not hardware vendors, it will be interesting to see if this feature takes off.