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eGPU benefit on internal monitor?


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#1 jgwdoc

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Posted 16 July 2018 - 07:44 PM

I'm a little confused by the various Apple support documents on the new Blackmagic eGPU. It seems like it only provides acceleration for applications run on an external monitor?
Is there any benefit if you're trying to run an application (game) on the internal monitor of a MBP?  Is there a way to tell the MBP to use the external GPU for all functions?
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#2 Cougar

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Posted 16 July 2018 - 08:46 PM

Only internal GPUs can power internal monitors. There's kind of sort of a way around this, but it requires developers to add support for it and it would hurt performance. See "Internal Display" here: https://9to5mac.com/...-of-egpu-video/

#3 jgwdoc

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Posted 16 July 2018 - 09:41 PM

Thanks. That was my impression, but some of the commentary on the Apple support site is confusing. It seems like there are a few hacks that might essentially fool the machine into thinking the internal monitor is actually external, but probably not worth the trouble and might crash with each OS update.
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#4 Sneaky Snake

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Posted 17 July 2018 - 03:55 PM

Even if it works your performance is significantly worse compared to an external monitor. The reason being that the TB cable has limited bandwidth and if you have to pipe all of the display data back over the TB cable to your internal screen it uses up some of that precious bandwidth.

Internal Display data path: Computer -> TB cable -> eGPU -> TB cable -> Internal Display
External Display data path: Computer -> TB cable -> eGPU -> HDMI/DP -> External Display

Various benchmarks of eGPU's on Youtube (Razer Core for example) showcase this performance loss.
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#5 jgwdoc

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Posted 18 July 2018 - 09:55 PM

The thing I find confusing is whether applications run on the internal screen of the MBP are themselves able to use the external GPU, regardless of whether the internal screen is accelerated or not? Perhaps my question just reflects my ignorance, but is the eGPU only able to accelerate applications that output through an external screen?
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#6 jgwdoc

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Posted 15 October 2018 - 07:49 PM

So, it seems like there are a growing number of ways to make this work, either with an internal or external monitor.
I'm considering getting a Sonnet eGFX Breakaway box and throwing a Radeon Vega 64 card in there ('cause Apple still doesn't play nice with NVIDA), and then maybe throwing in a 4k external monitor.
Have any of you tried this yet?  There a number of ways described at on-line forums to make this work under Bootcamp, as despite having a souped up card it seems that the framerate benefits on the Mac side remain limited. This limitation may well be driver related. Perhaps one of you has a trick for downloading updated drivers to the Mac side instead being stuck with Software Update?
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#7 ozzy

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Posted 16 October 2018 - 04:22 PM

Have you checked out egpu.io? I haven't used an AMD eGPU, but I use an nVidia one with my 2012 MBP in both Mac OS and Bootcamp. Nvidia is definitely a bit of a PITA in OS X and requires the amazing work of a few developers on the egpu.io forum, but AMD is supported natively in 10.13.4+ and 10.14. Bootcamp I think is a bit trickier with AMD.

Egpu.io has a whole database of people's build and how they did it and the results, searchable by GPU type, OS X vs Windows, Mac type, etc. Hopefully someone in there has the config you are looking to do.

#8 jgwdoc

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Posted 17 October 2018 - 06:05 PM

Thanks ozzy, I have been looking at egpu.io.  I'm trying to avoid situations where each software update breaks my set-up and requires another hack, but there seem to be a number of ways to make this work. I was just curious as to whether anyone on IMG had tried it yet. It seems to be the only way to adapt a mac laptop to the demands of new AAA games. Sadly, these days almost everything I play is via Bootcamp, so smooth functionality under Windows 10 is key.
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#9 ozzy

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Posted 18 October 2018 - 01:16 PM

I definitely understand. In that case AMD is the only way to go for Mac functionality (assuming you have a TB3 Mac), as it is natively supported. I would just check out some of the egpu.io reports for AMD functionality on your model in Bootcamp to make sure it isn't a problem.

And I agree with how easy this is to setup in Bootcamp and how much better frame rates are. That being said, some metal games have really improved their performance. Hitman is very good on the Mac, and Rise of the Tomb Raider plays incredible well on OS X using my eGPU 1070 and my 6+ year old MBP (with only TB1). I benchmark at ~42 FPS on ultra settings at 1440p in OS X, and about ~46 FPS on the same ultra settings in 1440p on Windows.