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DX12 GPU Combo

#1

I’m not sure how many people remember this, but way back when DirectX 12 was first shown off there rumors floating around that the up coming DX12 API would allow for the combination of AMD and Nvidia GPUs in a single system treating it all as just a pool of graphical processing power. This was incredibly intriguing and the implementation of such a feature would allow for a much more gradual upgrade process over the years by being able to add a new GPU while only parting with the oldest or slowest one in the system.

Fast forward to now, and obviously no such feature has been created or implemented within DX12 nor any other graphics API (to my knowledge). What I am seeking via this post is if anyone knows of any tech, projects, or tools that could facilitate such an interesting technical feat since this topic seems to have died along with the rumors floating around in 2015.

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#2

Vulkan supports this and I believe DX12 does too. The catch is that it’s not automatic. Engine developers have to explicitly use all GPUs and split the work between them.

In practice engines rarely do this because there’s just not enough dual-GPU systems out there to warrant the additional work and testing.

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#3

Well that’s pretty worthless. That’s the whole reason SLI and CrossFire are horrible because both require the developers of the game or software to code for it rather than it just being something handled by the graphics driver or the rendering API.

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#4

That’s exactly what SLI and Crossfire do. Developers program as if there was only a single graphics card and the driver takes care of the rest. Because it’s handled by the driver is also why cards from different manufacturers - and thus drivers - don’t work together.

Instead of simulating one GPU Vulkan/DX12 give developers access to all devices, but in turn don’t split up work automatically.

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#5

Pretty sure this is usable under certain conditions and I am sure i have seen a video that tested it. LTT perhaps?

Either way, dual gpu is generally more trouble than it is worth. I say that as a former vega crossfire user (didn’t buy specifically for crossfire, but tried it out for shits and giggles. and annoyance).

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#6

The benefit of SLI/crossfire is the game developer doesn’t need to code for it. Explicit multi-GPU in DX12/Vulkan is the opposite, the game must support that functionality. It supposedly works really well but as pFtpr correctly noted, nobody bothers because nobody has multiple GPUs anymore, in a catch-22 type thing.

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#7

If developing for multi-gpu could be a DLC or loot box that you pay extra for we might see it in more games

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#8

If they come up with a loot box for multi-gpu I’ll spend at least three whole days laughing my ass off

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#9

Honestly, all it would take is for Unity, Unreal, Snowdrop, and Frostbite to support explicit multi-GPU and the majority of games would inherit that.

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