Razer Core, SLI and Crossfire

[Nardella]

I want to see a LTT video attempting to get SLI and Crossfire running using a pair of external GPU boxes. Might have to cut holes in the boxes.

 

Not practical but probably amusing and interesting.

[Sniperfox47]

27 minutes ago, Nardella said:

I want to see a LTT video attempting to get SLI and Crossfire running using a pair of external GPU boxes. Might have to cut holes in the boxes.

 

Not practical but probably amusing and interesting.

Because of how the PCIe lanes work I doubt it would work for crossfire, and it definitely wouldn't work for SLI.

 

SLI *requires* 8 physically and electrically connected PCIe lanes to work while Thunderbolt 3 provides a max of 4.

 

And as far as Crossfire goes, because of how the DMA, plug and play, and other low level hardware support is handled, the cards would likely have issues communicating. I don't know how the low level interface for Crossfire works, but Thunderbolt messes with a lot of stuff that could interfere with that.

[Nardella]

Well I would like to see it attempted for Crossfire if there is a chance it will run, if only for the novelty.

 

As for SLI, if true, that is a shame.

[Nardella]

On 9/30/2017 at 3:40 PM, Sniperfox47 said:

Because of how the PCIe lanes work I doubt it would work for crossfire, and it definitely wouldn't work for SLI.

 

SLI *requires* 8 physically and electrically connected PCIe lanes to work while Thunderbolt 3 provides a max of 4.

 

And as far as Crossfire goes, because of how the DMA, plug and play, and other low level hardware support is handled, the cards would likely have issues communicating. I don't know how the low level interface for Crossfire works, but Thunderbolt messes with a lot of stuff that could interfere with that.

Has anyone actually tested to see for sure that SLI does not work with 4 PCIe lanes. Cause it may be that this is just "unsupported" in the sense that it hasn't been tested and is not expected to work well.

 

Also isn't there some fancy new API that allows multiple GPUs to work without SLI or Crossfire?

[Sniperfox47]

1 hour ago, Nardella said:

Has anyone actually tested to see for sure that SLI does not work with 4 PCIe lanes. Cause it may be that this is just "unsupported" in the sense that it hasn't been tested and is not expected to work well.

Yes. It literally does not work. If you take the PCIe slots and limit them to a 4x connection SLI will cease to function. On both Windows and Linux, regardless of the driver version or PCIe version (2.0 or 3.0).

 

1 hour ago, Nardella said:

Also isn't there some fancy new API that allows multiple GPUs to work without SLI or Crossfire?

And yes. Games written to render with DX12 or Vulkan can explicitly support multiple GPUs, handing out the workloads to each manually. This requires a ton of work from both the game engine, and the game itself.

 

Afaik multi-GPU support is currently only in 2 games (Ashes of the Singularity and Rise of the Tomb Raider) and is marked as "potentially unstable, use at your own risk" in both. And both of these are "benchmark" games designed to show off the new API.

 

This kind of multi-GPU would work with 2 Razer cores with no additional configuration, but it is also *very* different from SLI or Crossfire.

[Nardella]

13 minutes ago, Sniperfox47 said:

Yes. It literally does not work. If you take the PCIe slots and limit them to a 4x connection SLI will cease to function. On both Windows and Linux, regardless of the driver version or PCIe version (2.0 or 3.0).

 

And yes. Games written to render with DX12 or Vulkan can explicitly support multiple GPUs, handing out the workloads to each manually. This requires a ton of work from both the game engine, and the game itself.

 

Afaik multi-GPU support is currently only in 2 games (Ashes of the Singularity and Rise of the Tomb Raider) and is marked as "potentially unstable, use at your own risk" in both. And both of these are "benchmark" games designed to show off the new API.

 

This kind of multi-GPU would work with 2 Razer cores with no additional configuration, but it is also *very* different from SLI or Crossfire.

Great! LTT get working on that video please!