Very bad perfomance with external gpu.

[mihuil79]

Hello. Sorry for my English first. I am using latest dolphin, stable and beta and development versions and ishiiruka versions. I have got problem with perfomance of dolphin with external gpu (gtx 660). My PC is All-IN-One MSI, windows 10 x64,latest nvidia drivers, high perfomance power plan, i3-2100, 12 Gb DDR3 RAM, nvidia gt 540m and now i plug in external gpu through chinesse adapter. And my pc boost in pc games and other emulators. But dolphin works strange in 3d games (wii sport resort, super mario galaxy, punch out, etc). GTX660 100% usage and 30-35 fps. Even in 640x360 resolution. And fps doesnt change if i change resolution from 640x360 to hd or full hd. Without external gpu on gt540m same games works fine, even in hd resolution. So why external gtx660 works with dolphin much much worst then internal gt540m? For example cemu (wii u emulator) have good boost with external gtx 660 and use this gpu correctly but dolphin use this gpu 100% and give 30-40 fps even in 640x360 resolution.

1. FPS 30-40 doesnt change with changing resolution from 360p, 720p, 1080p.
2. 100% usage of gpu even with 360p resolution.
3. Same games works fine with gt540m even in 720p.
4. Other emulators and pc games have boost with external gpu.
5. FPS and perfomance doesnt change if i change backend (vulkan, directx 9,10,11).

Help me please. Its very strange situation.
P.S. Forget to say that gtx660 work through pci express x1 port 5gb/s. (WiFi port of my oc).

[JMC47]

It's due to coherent memory mappings over thunderbolt according to an expert.

[mihuil79]

(05-05-2020, 06:47 PM)JMC47 Wrote: It's due to coherent memory mappings over thunderbolt according to an expert.

Hello. What those this means? And what can i do with this?

[JMC47]

Use your internal GPU, it'll be faster. Because of CPU<->GPU communication, thunderbolt isn't fast enough even though the GPU is a bit stronger. Your internal GPU can communicate faster since it is directly connected to the motherboard.

[mihuil79]

(05-05-2020, 10:31 PM)JMC47 Wrote: Use your internal GPU, it'll be faster.  Because of CPU<->GPU communication, thunderbolt isn't fast enough even though the GPU is a bit stronger.  Your internal GPU can communicate faster since it is directly connected to the motherboard.

Sorry, but other emulators and pc games works much better with external gpu then with internal gpu. Only dolphin works very bad with external gpu. Something wrong with dolphin i think. For example need for speed the run works on gt540m in 1280x720 resolution and middle settings with 40-50 fps, but on external gtx660 it's works in full hd and extra settings with 60 fps. Or for example cemu with gtx660 can run games in hd or full hd with 60 fps, but with gt540m it can run same games in 360p with low fps. So i think it's not limit of pci express x1 port of external gpu, but something wrong with dolphin settings or dolphin code may be. Do you agree with me? It's too strange. Other games and emulators works much better with external gpu, but only dolphin works much worst with external gpu.