Terrible FPS with an external GPU

Question

I am running X Plane 11 on a MacBook Pro 2017. I have been getting 20-30 fps using the on board radeon pro 560.

So I thought I would try an eGPU with an RX 580 8GB which is now natively supported by High Sierra 13.3.3.

This seems to work ok for other software and GeekBench gets gpu score hitting 111k. Nearly 3 times to score of the onboard card.

But in X-plane it becomes unplayable even at lowest render settings with the eGPU. <10 fps with no objects and low effects and textures.

I know eGPUs are relatively new, so perhaps, hopefully it is a bug and X-plane can be further tweaked to support this.

Unless anybody has any other ideas.

Comments

I have the same issue on my 2017 MacBook Pro (onboard Radeon Pro 560 4GB). When I run X-Plane using the onboard GPU, I get about 20 - 25 fps. So I  decided to add an AKiTiO Node eGPU with Radeon RX 580 8GB. Now when running XP11 I get 10 +/- fps. 

When I run the Unigine Heaven Benchmark on both the onboard and eGPU and the eGPU with 2xAA and quality set to Ultra, resolution 1920x1080

On Board Radeon 560: averaged 21 fps 

eGPU with Radeon 580: averaged 46 fps

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I have the same issue on my 2017 MacBook Pro (onboard Radeon Pro 560 4GB). When I run X-Plane using the onboard GPU, I get about 20 - 25 fps. So I  decided to add an AKiTiO Node eGPU with Radeon RX 580 8GB. Now when running XP11 I get 10 +/- fps. 

When I run the Unigine Heaven Benchmark on both the onboard and eGPU and the eGPU with 2xAA and quality set to Ultra, resolution 1920x1080

On Board Radeon 560: averaged 21 fps 

eGPU with Radeon 580: averaged 46 fps

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I have now got it running in Bootcamp. In this case the eGPU does outperform the onboard gpu. It works pretty well with reasonably hight settings.

So there is definitely something wrong with X-Plane on MacOS with eGPU - it just doesn't work.

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I have the same issue on my 2017 MacBook Pro (onboard Radeon Pro 560 4GB) with eGPU Radeon RX 580 8GB. When Running XP11 I get 20+ fps with the onboard Radeon Pro 560 4GB but only 10 +/- with eGPU Radeon RX 580 8GB

Answer 1

We have actually talked directly with AMD about eGPUs. As best we understand, these must be used with an external monitor to accelerate graphics-apps like X-Plane on an iMac or laptop, so that the eGPU can feed the monitor directly. You may also need to set the external monitor to the 'main' monitor in system prefs too, if X-Plane keeps getting the wrong GPU.

Comments

I have iMac 5k which has onboard Radeon pro 580 and can get very good fps 40-50 with quality High(hdr), FXAA, objects medium & reflections low. But I decided to get e-gpu Sonnet (550w) and Radeon Vega 54 connected to external monitor as useing for UHD video work. Issue is I follow your instructions I have set application to use external GPU as per Apples instructions launch XP11 and under settings it still see’s onboard gpu as primary monitor and the external as monitor 1, so I updated settings to not use primary and to only use monitor 1 but I get terrible fps no better than 20fps. Running external benchmarks and the Vega 54 is averaging over 120fps @1440p & can also see final cut when I select use external gpu it does just that. So is there something that also needs modifying for XP11 to work properly with e-gpu?

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X-Plane uses OpenGL and Direct3D for its rendering APIs. On Macs, eGPUs are supported with apps that use the the Metal graphics API from Apple. Apple announced last year that OpenGL was being deprecated on the Mac. So unless the X-Plane team decides to adopt Metal external graphics on the Mac will be sub optimal. The good news though is that there is some work being started by the team on Vulcan and Metal which was posted last month. So fingers crossed for the future!