Use specific GPU for Reshade

Hi,
first thing hello to everybody and thanks Crosire and the shader developers for such a fantastic tool.

Do you think it would be possible to assign an specific GPU to handle the Reshade postprocesing? Some old games can't use SLI so for those with more than one GPU it could be useful to use the second GPU to render the reshade postprocessing pass so the the main graphics card gets more juice to handle the game itself.

Just an Idea. I have no clue if is even remotely possible or if it could bring any performance boost at all.

Regards.

ReShade uses the GPU the game uses. I haven't read myself into SLI etc. much, so I don't know if it's possible to share resources across the GPUs which would be required to do this.

Got it. Never mind then. It works great as it is anyway.

Thanks for the prompt response.
Regards.

Bump! Would this still be a possibility?

This would be really useful for those of us with a old GPU lying around or a decent IGP in the CPU (which I imagine is a good chunk of us).

even if this works, the additional bandwidth costs from moving frames from GPU to GPU, would erase any performance gains that this might create.

moriz1 wrote: even if this works, the additional bandwidth costs from moving frames from GPU to GPU, would erase any performance gains that this might create.

Crossfire moves frames over the PCIe bus, and it seems to work well enough.


There's an old piece of software called Lucid Virtu that did something similar. The idea was to use Intel IGPs to "offload" some of the work from the main GPU... That part was rubbish, of course, but the point is that it rendered the game on the main GPU with and piped it to the Intel IGP's video output without a big hit.

brucethemoose wrote:

moriz1 wrote: even if this works, the additional bandwidth costs from moving frames from GPU to GPU, would erase any performance gains that this might create.

Crossfire moves frames over the PCIe bus, and it seems to work well enough.


There's an old piece of software called Lucid Virtu that did something similar. The idea was to use Intel IGPs to "offload" some of the work from the main GPU... That part was rubbish, of course, but the point is that it rendered the game on the main GPU with and piped it to the Intel IGP's video output without a big hit.

crossfire frames are in the neighbourhood of 6-16.7 ms, depending on how fast the game is running. a ReShade preset typically finishes everything within 0.2 ms, even less if you don't run any of the heavy-hitter effects.

basically, because ReShade runs a few orders of magnitude faster compared to crossfire/sli, it is much more sensitive to latency effects introduced by bouncing frames across PCI-e.

moriz1 wrote:

brucethemoose wrote:

moriz1 wrote: even if this works, the additional bandwidth costs from moving frames from GPU to GPU, would erase any performance gains that this might create.

Crossfire moves frames over the PCIe bus, and it seems to work well enough.


There's an old piece of software called Lucid Virtu that did something similar. The idea was to use Intel IGPs to "offload" some of the work from the main GPU... That part was rubbish, of course, but the point is that it rendered the game on the main GPU with and piped it to the Intel IGP's video output without a big hit.

crossfire frames are in the neighbourhood of 6-16.7 ms, depending on how fast the game is running. a ReShade preset typically finishes everything within 0.2 ms, even less if you don't run any of the heavy-hitter effects.

basically, because ReShade runs a few orders of magnitude faster compared to crossfire/sli, it is much more sensitive to latency effects introduced by bouncing frames across PCI-e.

In essence, you'd be making the ReShade algorithm "free" (in terms of an fps hit) in exchange for ~1 frame of input lag.

So yeah, it'd only be worth it for heavier ReShade presets or slower hardware. But I know some of my presets go over 0.2ms. I can't afford that kind of FPS hit, but I can afford the latency hit.

Copying an entire frame over PCIe is slow, as in really slow (as mentioned). It can be affordable with current resolutions (720p, 1080p, but don't try to go higher) for when you do lots of work that greatly exceeds the copy time. And the copy needs to happen asynchronously or else you'll actually slow down rendering even more and not all hardware supports that.
But either way, this can't happen because DX11 and lower do not have API support for addressing different GPUs independently of each other. DX12 and Vulkan do, but ReShade does not support those anyway.