DirectX 12 rumoured to bring cross-vendor multi-GPU support

February 25, 2015 // 11:38 a.m.

Tags: #amd #api #crossfire #crossfirex #direct3d #direct3d-12 #directx #directx-12 #gpu #graphics #intel #microsoft #multi-gpu #nvidia #sfr #sli #windows-10

An anonymous source has claimed that Microsoft's upcoming DirectX 12 API will allow gamers to combine the power of multiple graphics cards even between manufacturers, bringing the possibility of combining AMD and Nvidia discrete graphics in a single gaming system for the first time.

Both Nvidia and AMD offer technologies - SLI in the former's case, CrossFire in the latter's case - which allow multiple GPUs to be used simultaneously in a single system. While the performance doesn't scale linearly with the number of GPUs, it offers a significant boost over a single GPU when properly supported in a game or engine and is used to power the companies' top-end dual-GPU graphics cards. For AMD, the technology is also used to allow owners of its accelerated processing units (APUs) to combine the integrated graphics hardware with selected discrete GPU models to create something more powerful than the sum of its parts.

SLI is SLI, and CrossFire is CrossFire, and before now never the twain have met. An anonymous source speaking to Tom's Hardware suggests that DirectX 12, the latest application programming interface (API) from Microsoft, will change all that and allow GPUs from multiple vendors to be combined in a single system. The secret: Explicit Asynchronous Multi-GPU.

Previous details released regarding DirectX have suggested that the API will allow developers to get closer to the metal than ever before, and AMD itself has hinted that changes to the way DirectX operates will allow multi-GPU setups to make better use of the combined memory. Now, it is being claimed that any and all GPUs in a system will be combined using a technology dubbed Split Frame Rendering which is closer to the original implementation of SLI by 3dFX than Nvidia's similarly-named equivalent. Under SFR, it is claimed, GPUs can cooperate on a single frame rather than rendering alternate frames. By pushing some rendering tasks to one GPU and others to another, there's no need to keep a copy of all data in both GPU's VRAM - which is how DirectX, as AMD promised, will free up more memory in multi-GPU scenarios.

The unnamed source, which did not name-drop DirectX 12 directly and instead referred to an 'unspoken API,' claims that a move to SFR will allow GPUs from multiple vendors to operate in concert. As well as allowing a gamer to fit a system with both AMD and Nvidia GPUs - potentially allowing a game to take advantage of technologies exclusive to each simultaneously, using both AMD's TressFX and Nvidia's PhysX for but one example - the shift would allow systems to make better use of integrated graphics capabilities on modern CPUs to further boost performance, letting an Intel CPU's graphics hardware lighten some of the load from an AMD or Nvidia discrete graphics card for example.

The site's source claims that there is one small catch, however: when it comes to optimising for workload spreading, it will be left to each engine or game developer individually. This means that in order for a game to take full advantage of SFR and the new vendor-agnostic multi-GPU rendering, developers will have to explicitly add support.

Neither Microsoft, Intel, AMD nor Nvidia have commented on the source's claims.
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