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lowenz

TDM and Optimus-like technology on desktop systems

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Maybe you don't know but the last iterations of Windows 10 on multi-GPU systems automatically choose the "best" GPU for the rendering (in D3D11 and lastest OpenGL applications) enabling the possibility of an Optimus-like configuration on desktop systems too: the active AND single-showed desktop on the monitor connected to the iGPU (the "integrated" GPU on the processor chip) where the output of the "real working" (typically dedicated, on the classic PCI-Express card) GPU is eventually routed thanks to the framebuffer being copied through the main System Memory.

The results (so you can see the actual overhead of the framebuffer copying/swapping process )

Pure Dedicated GPU (GeForce 1050 Ti):

0.jpg

"Optimus-Like" configuration (Intel HD 630 + GeForce 1050 Ti)

1.jpg

 

Not bad! Only a 9.5% of performance hit on a system with DDR4 2400 (so with better RAM modules and IMC you can reduce it to 5% I think)

Of course you can always force the rendering GPU through the dedicated interface in  "Display Settings -> Graphic Settings"

Edited by lowenz

Task is not so much to see what no one has yet seen but to think what nobody has yet thought about that which everybody see. - E.S.

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19 hours ago, lowenz said:

Maybe you don't know but the last iterations of Windows 10 on multi-GPU systems automatically choose the "best" GPU for the rendering (in D3D11 and lastest OpenGL applications) enabling the possibility of an Optimus-like configuration on desktop systems too: the active AND single-showed desktop on the monitor connected to the iGPU (the "integrated" GPU on the processor chip) where the output of the "real working" (typically dedicated, on the classic PCI-Express card) GPU is eventually routed thanks to the framebuffer being copied through the main System Memory.

The results (so you can see the actual overhead of the framebuffer copying/swapping process )

Pure Dedicated GPU (GeForce 1050 Ti):

0.jpg

"Optimus-Like" configuration (Intel HD 630 + GeForce 1050 Ti)

1.jpg

 

Not bad! Only a 9.5% of performance hit on a system with DDR4 2400 (so with better RAM modules and IMC you can reduce it to 5% I think)

Of course you can always force the rendering GPU through the dedicated interface in  "Display Settings -> Graphic Settings"

Good to hear things are moving in that direction but 10% (1.5msec) is un-explainable slow

1080p framebuffer is just 8MB of data. That means the effective transfer speed is ~5GB/sec. Meh!

Compare to promised ~15GB/sec for PCIEx16 3.0. Unless, of course, you're running in x8 or 2.0 mode.

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3.0 x16 here!

But DDR4 2400 only.


Task is not so much to see what no one has yet seen but to think what nobody has yet thought about that which everybody see. - E.S.

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2 hours ago, lowenz said:

3.0 x16 here!

But DDR4 2400 only.

Dual channel? That's what 40GB/sec?

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Dual channel yes, but the limitation resides in the IMC and PCI-E management as you say. Still more speed (latencies are already low in my system) in the memory section could gives more clear results.


Task is not so much to see what no one has yet seen but to think what nobody has yet thought about that which everybody see. - E.S.

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I can confirm all is working as intended !

I've literally unplugged the GeForce from the monitor input but I'm getting some solid 55-56 FPS in TDM 😛 (in the scene above)

With NO wizardry in Windows at all, it's just there.

Edited by lowenz

Task is not so much to see what no one has yet seen but to think what nobody has yet thought about that which everybody see. - E.S.

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Does not work the other way around

When monitor is plugged to the nVidia, it won't use the IGP even though configured in Settings :(

Job half-done, as always with M$

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Good old Source (SDK 2013 Single Player Upcoming branch), all maxed out (MSAA 4x too), with 999 FPS cap

Pure Dedicated GPU (Radeon RX 570 / 2050 MHz VRAM) -> 548 FPS

Optimus-Like configuration (Intel HD 630 + Radeon RX 570/ 2050 MHz VRAM ) -> 379 FPS

 

So the overhead is (548-379)/548= 31%

Edited by lowenz
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Task is not so much to see what no one has yet seen but to think what nobody has yet thought about that which everybody see. - E.S.

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With modern engine like the Unreal Engine 4 in Borderlands 3 the overhead is 0 (yes, ZERO)

So maybe the main issue is the texture streaming optimization missing in old engines?

 

Borderlands 3 has the same average framerate in the integrated benchmark!

Edited by lowenz

Task is not so much to see what no one has yet seen but to think what nobody has yet thought about that which everybody see. - E.S.

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