Clarification on using Mac's 5K monitor
 
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Clarification on using Mac's 5K monitor  

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Budmas
(@budmas)
New Member
Joined: 4 months ago
 

Hi Everyone!

I've searched the forums and Googled the hell out of everything I could to find the answer to my questions before deciding to post this. Maybe you guys can help clarify what I might be able to purchase and use. I have a late 2015 Imac 5K with the Intel 3.2GHz and M390 2GB GPU, equipped with TB2. I've upgraded my OS to Catalina (10.15). From everything I've found, I can run a Radeon RX580 into one of the many enclosures you guys recommend (Akitio Thunder3 is what I'm looking at), preferably a TB3 enclosure using the Apple TB3 to TB adapter. The reason for an egpu for myself is for use with Davinci Resolve, which I know will allow an egpu to be used once it's set up.

I've searched the build links you guys have and no one currently shows the same computer running on Mac OS with Catalina (looks like all the guys are running Windows on the Boot Camp side on this computer, unless I've overlooked some). Either way, the confusion for me comes in when using the monitor. I'd like to use my Mac's 5k monitor and I don't want to use an external monitor. I'm seeing some sites say that I need a 4K dummy plug (for lack of a better term) and that an egpu will not work with my Mac's monitor. Can you guys clarify if this is true? Also, I've noticed a lot of notes on this site about the Beta builds of Catalina, but I'm not positive if anyone is having good results with the current release build of Catalina?

I'd like to start purchasing the parts, but I'd hate to buy them only to find out that I can't use my Mac's monitor and would have to purchase an external monitor to take advantage of the egpu. Any information and advice would be appreciated! Thank you in advance!

Budmas

 

2015 iMac 5K, 3.2Ghz, M390, TB2, Mac OSX Catalina 10.15


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joevt
(@joevt)
Noble Member
Joined: 2 years ago
 

@budmas Catalina beta is only needed for RX 5700XT.

The iMac has a M390 dGPU. This will give problems trying to run eGPU to internal display in Windows. But you're using macOS so that should be ok.

TB2 is not fast enough for 5K60 so you'll either get a lower refresh rate, or you should limit the resolution to 4K or lower. But you're not doing gaming, so this is also ok - let the M390 draw the UI to the internal screen while the dGPU does compute for Davinci Resolve. You won't need a 4K dummy plug for that.

Search for other builds with an AMD dGPU (such as MacBook Pros) and eGPU. Also google Davinci Resolve and eGPU:
https://9to5mac.com/2018/04/19/macos-egpu-performance-test-davinci-resolve-video/
I'm not sure how TB2 will affect things.

Mac mini (2018), Mac Pro (Early 2008), MacBook Pro (Retina, 15-inch, Mid 2015), GA-Z170X-Gaming 7, Sapphire Pulse Radeon RX 580 8GB GDDR5, Sonnet Echo Express III-D, Trebleet Thunderbolt 3 to NVMe M.2 case


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Budmas
(@budmas)
New Member
Joined: 4 months ago
 

@joevt

Thanks for the information and clarification. Your information brings up another question. So, since the TB2 can't reproduce the 5k @60Hz and if I allow my internal GPU to take the UI task, I can still be in 5K resolution for everything, but the egpu will take the Davinci processing? Or is it that I have to bring everything down to a 4k resolution, including my desktop? Thank you in advance!

 

Budmas

2015 iMac 5K, 3.2Ghz, M390, TB2, Mac OSX Catalina 10.15


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joevt
(@joevt)
Noble Member
Joined: 2 years ago
 

@budmas It should be fine. The 5K resolution will not affect Davinci processing.

Mac mini (2018), Mac Pro (Early 2008), MacBook Pro (Retina, 15-inch, Mid 2015), GA-Z170X-Gaming 7, Sapphire Pulse Radeon RX 580 8GB GDDR5, Sonnet Echo Express III-D, Trebleet Thunderbolt 3 to NVMe M.2 case


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