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iMac (Retina 5K, 27-inch, Late 2015) with External 4k Monitor
 

iMac (Retina 5K, 27-inch, Late 2015) with External 4k Monitor  

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tritus
(@tritus)
New Member
Joined: 11 months ago
 

Hey, 

I have been looking everywhere for the best solution regarding eGPUs and how compatible it would be with my current computer. I have bootcamp installed and I am just trying to understand which eGPU would be best for my situation. I am looking to game on my external monitor. I don't really care about running the games on the 5k internal display. How would I go about making sure I buy the right things? Is it even possible to get an eGPU for my iMac? Should I use bootcamp to run my external monitor? All suggestions would help. 
I know I am going to need a T3 to T2 adapter, anything else?

My build:

4 GHz Intel Core i7

24 GB 1600 MHz DDR3

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


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Jyin
 Jyin
(@jyin)
Estimable Member
Joined: 2 years ago
 

For a while I used to use the 2015 iMac 5K with eGPU.

It worked well enough, but that was over a year ago, since then I moved to 2017 iMac 5K.

I understand that since when I used it on 2015 iMac, Apple have dropped support for TB2, and you will require a hack to make it work now.

 

You should pick the GPU you want before you start looking for eGPU.

Your choice of GPU may narrow down the choice of eGPU, due to size and power requirements.

You may even need to mod the eGPU to meet your GPU.

Unless you have eGPU specific needs (looks, portability, noise, cost, etc), picking the GPU will help with the decision.

 

For picking GPU, you want to decide which OS you want your focus to be.

If you want best experience with OS X, you want to go with AMD. The RX 580, Vega 56/64/FE is a good choice.

Personally, I had good luck with Vega FE/LC with my 2015 iMac 5K.

I had it up and running in OS X, as well as Bootcamp, but process was very complicated for Bootcamp. I was never able to get dGPU/iGPU working with eGPU in Bootcamp, so internal display only worked un-accelerated.

If you want best experience with Bootcamp, you may want to consider nVidia. You wont be able to use Mojave. But I hear nVidia has a driver for High Sierra. But only for 10-series or earlier, so no 20s (like RTX 2080 ti), if you want to use it in OS X at all.

I had good luck with RTX 2080 ti in Bootcamp with 2017 iMac 5K, except for the internal display being blank no matter what I did. I dont know how it will be with 2015.

 

For the eGPU, I have two Sonnet eGFX Breakaway Box 550s. Its roomy, easy to access, upgradable, modable, quiet and reliable. I particularly like its steel construction, so I was able to use magnetically attaching fans externally. Since the iMac doesnt need PD, I couldve gone with 350 (assuming you either dont need more power, or upgrade PSU), but I do have couple of MacBooks.

But there are other fine choices out there depend on your GPU pick.

The TB3 to TB2 adapter is only required if you get a TB3 based eGPU (I think you should, but you may find TB2 eGPU be cheaper).

This post was modified 11 months ago

2017 iMac 5k 27inch RP580 TB3 + Vega FE/LC + Sonnet 550 + EVGA GeForce RTX 2080 Ti FTW3 ULTRA GAMING + Sonnet 550 + Mac/Win10


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tritus
(@tritus)
New Member
Joined: 11 months ago
 

Thank you for your reply! 

I am looking into maybe a 1070 ti or Rx 580. How would I go about making sure it would work? You mentioned OS X compatibility. I am running High Sierra, would the eGPU register on my computer through the t3 to t2 cable? Or would I have to use boot camp? I’m also using an external monitor, would that be better? Assuming I buy the sonnet box and the RX 580 GPU, what would be the next step in terms of installation? Do I do it over OS X or through boot camp?

This post was modified 11 months ago

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


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Jyin
 Jyin
(@jyin)
Estimable Member
Joined: 2 years ago
 
Posted by: tritus

Thank you for your reply! 

I am looking into maybe a 1070 ti or Rx 580. How would I go about making sure it would work? You mentioned OS X compatibility. I am running High Sierra, would the eGPU register on my computer through the t3 to t2 cable? Or would I have to use boot camp? I’m also using an external monitor, would that be better? Assuming I buy the sonnet box and the RX 580 GPU, what would be the next step in terms of installation? Do I do it over OS X or through boot camp?

Both the RX 580 and 1070 ti ‘should’ work in OS X (HS) and Win10 (Bootcamp), but either way you will need to do some work to get around hurdles. You will be using the TB2 cable, and the TB2-TB3 adaptor if you choose an eGPU with TB3 like Sonnet BB550.

You want to start your research here:
https://egpu.io/forums/mac-setup/automate-egpu-efi-egpu-boot-manager-for-macos-and-windows/
https://egpu.io/forums/mac-setup/script-enable-egpu-on-tb1-2-macs-on-macos-10-13-4/
https://egpu.io/forums/pc-setup/fix-dsdt-override-to-correct-error-12/

For an older Macs like yours, there are no guarantees. Any solution you may find is nothing more than a hack (good ones, but you should be aware you are on your own if things go wrong). One of the reasons I decided to get 2017. The DSDT hack I had to do to get my Vega FE/LC on Bootcamp(which you will probably need if you pick RX 580) is the other reason. The 1070 ti will have different set of issues, but I have zero experience with 10-series. 

The external monitor is strongly recommended, and in case of iMacs with Bootcamp, required. 

For the actual process of installation, hardware parts should be easy.
For OS X, you will be dealing with Apple’s policy to block TB2 from recognizing an eGPU, and sub-par driver if you get nVidia (AMD cards generally work better here)
For Bootcamp, you will be dealing with Windows’ inability to allocate resources correctly (for AMD, nVidia tends to be better), and the usual driver issues.

J

This post was modified 11 months ago

2017 iMac 5k 27inch RP580 TB3 + Vega FE/LC + Sonnet 550 + EVGA GeForce RTX 2080 Ti FTW3 ULTRA GAMING + Sonnet 550 + Mac/Win10


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