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Multi-GPU doesn't exist for anything other than ML or HPC. While Vulkan fully supports it. Metal and DX12 don't. The real issue for real time AR/VR/144FPS+ is

Multi-GPU doesn't exist for anything other than ML or HPC. While Vulkan fully supports it. Metal and DX12 don't. The real issue for real time AR/VR/144FPS+ is knowing what you can/can't offload, what's the transfer latency, etc. this will change based on cards, generations, CPU's, library versions, Driver versions, vendors. It is a nightmare. Even SLI/XFire when you know there are identical cards, and drivers. You still see ~10-20% pref gain for 50% more resources.

eridius 9y ago
Metal 2 supports external GPUs. I don't know if this means it supports using multiple GPUs at once though.
jandrese 9y ago
I've wondered if it would be possible to design a dual GPU setup to handle VR applications more efficiently? VR tends to be kind of hard on current GPUs due to needing to render the scene from two viewpoints. With a dual GPU setup you could effectively dedicate one GPU per eyeball.
- spectralblu 9y ago
  That's actually not true. I believe with the latest generation of Nvidia cards (10 series) they made rendering multiple similar viewpoints dirt cheap by tweaking the hardware and the rendering pipeline. From the arstechnica review on the 1060: "GPU Boost 3.0, Fast Sync, HDR, VR Works Audio, Ansel, and preemption make a return too , as well as the ability to render multiple viewpoints in a single render-pass." https://arstechnica.com/gadgets/2016/07/nvidia-gtx-1060-review/ https://arstechnica.com/gadgets/2016/07/nvidia-gtx-1060-revi... From my limited understanding, VR is difficult because of the tolerances required. For regular gaming, slight frame drops were annoying, but didn't break the experience. Thus, it was reasonable to ship a game that was able to hit 60fps 99% of the time, and just write off the remaining 1% of the time. For VR, not only do we need to hit at least 75fps, the tolerance for frame drops is much much lower (a stutter while you're watching a monitor is annoying, the same stutter in VR could make you lose your balance). To aim to hit 75fps and guarantee that you'll hit that 99.9%, 99.99%, or 99.999% of the time is where the difficulty lies. I'm sure most of the HN audience has experience with just how difficult it is to tack on an additional 9.
seanp2k2 9y ago
in gaming, the gains are more like ~20-90% : http://www.babeltechreviews.com/gtx-1080-ti-sli-performance-25-games/3/ http://www.babeltechreviews.com/gtx-1080-ti-sli-performance-... Another more well-known source: https://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_1080_SLI/20.html https://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_1080_... at 3840x2160 there was an average of 171% performance across games when they excluded the ones which didn't scale with SLI at all.
carroccio 9y ago
100% more resources

eridius 9y ago

Metal 2 supports external GPUs. I don't know if this means it supports using multiple GPUs at once though.

jandrese 9y ago

I've wondered if it would be possible to design a dual GPU setup to handle VR applications more efficiently? VR tends to be kind of hard on current GPUs due to needing to render the scene from two viewpoints. With a dual GPU setup you could effectively dedicate one GPU per eyeball.

spectralblu 9y ago
That's actually not true. I believe with the latest generation of Nvidia cards (10 series) they made rendering multiple similar viewpoints dirt cheap by tweaking the hardware and the rendering pipeline. From the arstechnica review on the 1060: "GPU Boost 3.0, Fast Sync, HDR, VR Works Audio, Ansel, and preemption make a return too , as well as the ability to render multiple viewpoints in a single render-pass." https://arstechnica.com/gadgets/2016/07/nvidia-gtx-1060-review/ https://arstechnica.com/gadgets/2016/07/nvidia-gtx-1060-revi... From my limited understanding, VR is difficult because of the tolerances required. For regular gaming, slight frame drops were annoying, but didn't break the experience. Thus, it was reasonable to ship a game that was able to hit 60fps 99% of the time, and just write off the remaining 1% of the time. For VR, not only do we need to hit at least 75fps, the tolerance for frame drops is much much lower (a stutter while you're watching a monitor is annoying, the same stutter in VR could make you lose your balance). To aim to hit 75fps and guarantee that you'll hit that 99.9%, 99.99%, or 99.999% of the time is where the difficulty lies. I'm sure most of the HN audience has experience with just how difficult it is to tack on an additional 9.

seanp2k2 9y ago

in gaming, the gains are more like ~20-90% : http://www.babeltechreviews.com/gtx-1080-ti-sli-performance-25-games/3/ http://www.babeltechreviews.com/gtx-1080-ti-sli-performance-... Another more well-known source: https://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_1080_SLI/20.html https://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_1080_... at 3840x2160 there was an average of 171% performance across games when they excluded the ones which didn't scale with SLI at all.

carroccio 9y ago

100% more resources