Possible to use eGPU and LG 5K for gaming?
 
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Possible to use eGPU and LG 5K for gaming?  

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Mulvone
(@mulvone)
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Joined: 2 years ago
 

Sorry, I’m still pretty new to eGPUs but I was wondering if to have your monitor accelerated by the eGPU, if you can have both the eGPU and LG 5K ultrafine plugged into different TB3 ports or if the monitor needs to be directly connected to the graphics card. It’s a TB3 only model and I’m pretty sure there aren’t any TB3 port graphics cards on the market. Is there any possible way to have an eGPU accelerate a LG 5K so I can actually somewhat game on it and not have to use the internal display? Thanks

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gero
 gero
(@gero)
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Joined: 2 years ago
 

Currently, developers have to enable that functionality explicitly, because transferring the render result for each rendered frame to system memory via Thunderbolt and then to either the integrated display or a display connected to the Mac directly puts heavy load on the bus and unnecessary load on the system as whole.
For low resolution displays it might not be too much of a problem, considering Thunderbolt 3's high bandwidth, but 5K resolution means 5120 x 2880 * 4 (color depth for 32-bit RGBA in bytes) = 58,982,400 Bytes = 59 MB per Frame. This for a desired 60 frames a second is about 3.5 GB/s which is about the full bandwidth of current Thunderbolt 3 devices and would result in high CPU load and significant performance loss since data cannot be transferred from eGPU to display directly.
You should also consider the added latency that is inferred by the transfer from eGPU to RAM/CPU to display.

For more info on Apple's opinion about graphics rendering on eGPUs see  https://developer.apple.com/documentation/metal/advanced_techniques/device_selection_and_fallback/device_selection_and_fallback_for_graphics_rendering/

Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts


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