cancel
Showing results for 
Search instead for 
Did you mean: 

Why no SLi or Crossfire Support?

silent_wolf
Explorer
Just want to rant about the No SLi or Crossfire support from the ground up. Why limit the technology to just the processing power of the one card instead of n cards?  What was the logic behind the decision made at that point?

It just pisses me off when developers limits themselves like this. I wonder how much more would that have taken just to develop the SDK with SLi/Crossfire support from the beginning?

Anyhow, I would no doubt, move to a developer that support SLi/Crossfire first. Hopefully either HTC or OSVR are exploring these paths.

All I want is VR to be out of this single card cage!! We need better graphics for VR now.. 
20 REPLIES 20

Dreamwriter
Rising Star
Standard SLI is horrible for VR, it adds quite a bit of latency because of the way it's designed. nVidia has a new type of SLI coming out, VR SLI, which solves this by having each card render one eye rather than each card render every other frame. But VR SLI needs to be specifically supported by the developer, and nVidia has been slow to get the SDK to VR developers. 

silent_wolf
Explorer


Standard SLI is horrible for VR, it adds quite a bit of latency because of the way it's designed. nVidia has a new type of SLI coming out, VR SLI, which solves this by having each card render one eye rather than each card render every other frame. But VR SLI needs to be specifically supported by the developer, and nVidia has been slow to get the SDK to VR developers. 


Thank you for the explanation. Hopefully SLI/Crossfire gets fast tracked by one of the developers. Sony (PS4 Pro) should be the first to explore this I think since its roughly a crossfire setup.

cybereality
Grand Champion
Do some research on SLI on this forum. The topic has been beaten to death. It currently doesn't work at all, and it probably won't work for a while. In theory, it may be possible but would require very special programming (e.g. Nvidia VR SLI) and won't be an automatic thing that will just work in any game.
AMD Ryzen 7 1800X | MSI X370 Titanium | G.Skill 16GB DDR4 3200 | EVGA SuperNOVA 1000 | Corsair Hydro H110i Gigabyte RX Vega 64 x2 | Samsung 960 Evo M.2 500GB | Seagate FireCuda SSHD 2TB | Phanteks ENTHOO EVOLV

silent_wolf
Explorer


Do some research on SLI on this forum. The topic has been beaten to death. It currently doesn't work at all, and it probably won't work for a while. In theory, it may be possible but would require very special programming (e.g. Nvidia VR SLI) and won't be an automatic thing that will just work in any game.



Thanks for your response. I have read some older threads on the forum, it just seems that Oculus has already shut the door on SLI. You seem to prefer go the one card route in the other threads too. So I'm concerned the path Oculus is taking thats all. As a matter of fact, some game developers have already integrated the VR SLI to their engines and working, anyhow when the time comes lets hope nothing goes wrong at the Oculus end when the ball is in your court.. (lol, hers to hoping)

Just make sure the CV1 is ready for the games that DO support VR SLI

cybereality
Grand Champion
It's not up to Oculus to support SLI but to game developers (or, rather, engine developers). The issue is that traditional multi-GPU rendering (AFR) is horrible for VR and just won't work. So engine developers need to create custom rendering schemes and most don't bother for a small niche market. Even multi-GPU for 2D games is slowly fading away as more of the onus goes to developers with limited time and budgets. And, even in the best case, multi-GPU will add some amount of latency, so you could end up with a worse experience. Though it's not impossible, so maybe one day it will work.
AMD Ryzen 7 1800X | MSI X370 Titanium | G.Skill 16GB DDR4 3200 | EVGA SuperNOVA 1000 | Corsair Hydro H110i Gigabyte RX Vega 64 x2 | Samsung 960 Evo M.2 500GB | Seagate FireCuda SSHD 2TB | Phanteks ENTHOO EVOLV

silent_wolf
Explorer


It's not up to Oculus to support SLI but to game developers (or, rather, engine developers). The issue is that traditional multi-GPU rendering (AFR) is horrible for VR and just won't work. So engine developers need to create custom rendering schemes and most don't bother for a small niche market. Even multi-GPU for 2D games is slowly fading away as more of the onus goes to developers with limited time and budgets. And, even in the best case, multi-GPU will add some amount of latency, so you could end up with a worse experience. Though it's not impossible, so maybe one day it will work.


Thanks again for the response. Yes the AFR is old tech not designed for VR. However, the newer SLI tech for VR is already making headway and working, for example Nvidia Funhouse demo, DOOM VR, Fallout VR.. which are good signs, it'll be encouraging to see if Oculus would change their stance on the SLI tech and push to optimize it further. 



Atonnis
Explorer


Just want to rant about the No SLi or Crossfire support from the ground up. Why limit the technology to just the processing power of the one card instead of n cards?  What was the logic behind the decision made at that point?

It just pisses me off when developers limits themselves like this. I wonder how much more would that have taken just to develop the SDK with SLi/Crossfire support from the beginning?

Anyhow, I would no doubt, move to a developer that support SLi/Crossfire first. Hopefully either HTC or OSVR are exploring these paths.

All I want is VR to be out of this single card cage!! We need better graphics for VR now.. 


For now, it's not just better to disable SLI completely and then use the second card as dedicated to PhysX.

The difference is actually very noticeable.

Dreamwriter
Rising Star




It's not up to Oculus to support SLI but to game developers (or, rather, engine developers).

it'll be encouraging to see if Oculus would change their stance on the SLI tech and push to optimize it further. 



Why do you keep saying that? Are you being a troll? Multiple times in this thread it has been pointed out, including from an Oculus employee in a statement that you quoted just now, that Oculus has nothing to do with SLI. They have no stance to change. VR SLI is up to nVidia and developers, and game-engine developers, to support. Not Oculus. If I write a game using nVidia's VR SLI SDK, it will work on Oculus Rift. However, right now that's incredibly hard to do because nVidia/Unity/Unreal/Crytek have yet to officially integrate VR SLI into the most popular game engines. 

Zenbane
MVP
MVP


Why do you keep saying that? Are you being a troll?


He could be a Bot. His posts suddenly appear very scripted.