mid-2011 21.5" iMac HD6750M + GTX [email protected] (AKiTiO Thunder2) + macOS10.13 & Win10 [NayChan]^  


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September 6, 2017 1:12 am  

This guide is for the 21.5" Mid-2011 iMac 2.5Gh with discrete AMD Radeon 6750m.

I have been using this setup since November 2016 (nearly 10 months at time of posting).

Before Nvidia released Pascal web driver support for macOS I only used the eGPU for gaming in Windows 10 using BootCamp.

After macOS support was released I have not booted back into Windows for anything save upgrading to the Creators Update and DirectX 12 games since they are not yet fully supported in Wine.

This setup has been in constant daily use with macOS Sierra since April 2016 (nearly 6 months at time of posting). I have never attempted to get the internal screen working.

NOTE: I do not use a molex connector or external power supply. I use a regular universal AC adapter which came with an assortment of connectors and has a voltage switch for 12 volts. The graphics card I use receives all its power from PCIe slot and does not require a six or eight pin connector. If your card is not the same as mine (EVGA GTX 1050ti SC 4GB) then make sure that its maximum power draw does not exceed 75 watts. People might go ape bananas over this saying that the PCIe slot in the Thunder2 only allows 25 watts through but they are wrong. I saw one of the engineers working at AKiTiO confirm that the Thunder2 does in fact deliver 75 watts over PCIe while discussing the differences they implemented for the OWC Helios on some forum somewhere ( https://egpu.io/forums/thunderbolt-enclosures/75w-from-slot-on-the-akitio-thunder-2/). I must reiterate that I have been using this setup for nearly 10 months on a daily basis. Using a normal AC adapter the Thunder2 automatically turns on at boot and turns off at shutdown. Just make sure your AC adapter is 90 watts or more and can be set to 12 volts. This gives 75 watts for graphics card with the remaining left over for the Thunder2 board and Thunderbolt cable. Using a normal ac adapter the Thunder2 automatically turns on at boot and turns off at shutdown. Just make sure your AC adapter is 90 watts or more and can be set to 12 volts.


Hardware Used:

AKiTiO Thunder2

EVGA GTX 1050ti SC 4GB

Prudent Way 90W AC Power Adapter (AC90LE)

HP 27es Monitor


Software Used:

automate-eGPU.sh script by goalque         https://github.com/goalque/automate-eGPU

DisableMonitor by Tobias Salzmann         https://github.com/Eun/DisableMonitor

smcFanControl by Hendrik Holtmann         https://github.com/hholtmann/smcFanControl

iStat Menus by bjango         https://bjango.com/mac/istatmenus/

NOTE:  If you prefer a free alternative to iStat Menus then you can use HWSensors. I have personally never used it and have been using iStat Menus for years.         https://github.com/kozlek/HWSensors


1)  Unbox everything

2) Remove case from Thunder2 enclosure and install graphics card. I leave the case off the enclosure for increased cooling. This is really up to you and really depends on its location.

3)  Decide where to place the enclosure. I put a shelf/risor underneath my iMac and put the enclosure there. This enables line of sight and easy access for dusting. Make sure you put it somewhere that is protected from things that could fall and drinks that could spill.

4)  Plug AC adapter into electric outlet and then the Thunder2

5)  Plug Thunderbolt cable into Thunder2 and iMac

6)  Connect graphics card to external monitor using cable of choice


Installation (macOS):

1)  Download goalque's automate-eGPU.sh script and run it

2)  Follow instructions given by script to prepare macOS to use eGPU

3)  Restart

4)  Open System Preferences -> Displays and click on the 'Arrangement' tab. Setup the displays as they are on your desk and then drag the tiny white bar (representing the menu bar) onto the external monitor. This will make your external monitor the main display meaning that all apps launched on this monitor will be using the eGPU. If an app opens onto your iMac screen then it is most likely not using the eGPU but the discrete GPU inside the iMac.


If your iMac does not display the login screen or Desktop then you might need to hot plug during the boot process. After trying many different timing and methods I have finally settled on a way to hot plug during boot which works 99% of the time for my iMac. This is my process:

a)  Leave Thunderbolt cable plugged into iMac

b)  Turn on iMac

Again, if your iMac boots to login screen or Desktop then you are good and can continue on to Step 3. If you iMac reboots and displays a grey screen with a "Your computer restarted because of a problem" then you have most likely entered a boot loop.

c)  You may click the mouse to continue the boot process. If your iMac boots to the login screen or Desktop then you are good. If your iMac reboots and displays the grey screen with "Your computer restarted because of a problem" then unplug and continue to Step D.

d)  Unplug the Thunderbolt cable from your iMac and prepare yourself to quickly plug it back in.

e)  Use a mouse click to dismiss the paragraph screen and continue the boot process and immediately plug the Thunderbolt cable back into the iMac. It should now continue the boot process and display the login screen or Desktop.

If your iMac doesn't continue the boot process and reboots then unplug the Thunderbolt cable, click away the warning paragraph and plug the Thunderbolt cable in AS SOON as you see the Apple logo and before the progress bar displays. It might still work after the progress bar displays but doing it before is more reliable.

NOTE: I have a Do-It-Yourself Fusion drive setup with an aftermarket SSD and stock HDD so the timings for your setup might be slightly different. This is the process that works for my iMac.

When the Nvidia web drivers were released I had to do this hot plug process every time I booted my iMac. However, I now only have to do it every other week or so. If you encounter the grey screen with "Your computer restarted because of a problem then you'll most likely have to use the hot plug method.



Use Tobias Salmann's fantastic free app DisableMonitor to disable your iMac screen and use only your external monitor. This will ensure that your eGPU is being used to accelerate everything. The iMac screen will be disabled and the mouse will be restricted to your external display. The iMac screen will be black and the backlight will never turn off (this is normal).     https://github.com/Eun/DisableMonitor

When launching some fullscreen games the iMac screen will flash on and then off or even stay on. Just continue gaming as usual and after quitting these games the iMac screen will be enabled again. All you have to do is use DisableMonitor in your menu bar to disable it again.

iStat Menus can display the current temperatures in the menu bar of various components in your iMac. I have place the CPU temp reading in my menu bar to decide if I should increase the fan speeds. I also have the GPU temperature reading there but I am unsure whether it represents the discrete GPU or the eGPU.

If you find that your CPU is getting too hot then download smcFanControl and increase the fan speed. This app by Hendrik Holtmann is one of my essential Mac apps. I have always ran the fans on all my Macs a little higher than Apple standard. However, I suggest all those using an eGPU increasing the cooling of your CPU using this app.         https://github.com/hholtmann/smcFanControl

If you are gaming then I HIGHLY recommend increasing fan speeds. Apple does it automatically but they still tend to prefer quiet operation over cool components. I prefer to keep my CPU temp below 50℃ during normal operation and below 56℃ during gaming. This is overly cautious for the average user. I use the 'Step Up' profile for normal operations and 'Bit More' for gaming. The 'Midway' profile I created for exporting video when using apps that only use CPU for encoding and aren't accelerated by the GPU. You can choose to increase only the CPU fan. I raise the speed of all fans in case that helps the flow of air into and out of the iMac but I am unsure it makes any difference.


Installation (Windows):

1)  Install Nvidia drivers and shutdown with Thunderbolt cable unplugged.

2)  Plug Thunderbolt cable into iMac and boot. I never had to hot plug in Windows 10. If you just get a black screen then force restart by holding down the power button until your iMac turns off and then try again. It will eventually work.

3)  Change your Display Settings to 'Only display on Monitor #'. This should disable your iMac screen and turn off the backlight.

4)  Install EVGA Precision XOC and reduce 'Power Target' to 70%. I did this just to reduce the power draw over the PCIe slot in Windows. I don't know if it does this. It's just a better safe than sorry solution since I don't trust Windows.


Here are the Unigine Heaven Benchmarks:

I only did Extreme and High at 1920x1080 and 1600x900 since they resulted in 30FPS and 60FPS. I have been playing everything at 1920x1080 at Maximum settings without problems so far.

Here are the Geekbench results as well. First one is the discrete AMD Radeon HD 6750m 512mb with the second being the external Nvidia EVGA GTX 1050ti SC 4GB:


mid-2011 21.5" iMac HD6750M + [email protected] (AKiTiO Thunder2) + macOS10.13 & Win10

New Member
Joined: 1 year ago
Posts: 3
September 20, 2017 9:40 am  
Greetings @NayChan, 
I've installed an AORUS GTX 1070 Gaming Box on an iMac 21 "Finals 2015 fast and trouble free 
thanks to the Goalque guide from this review:
My doubts now are how to install the egpu in Windows 10.
How did you solve the thunderbolt driver installation in Windows 10?

Soon I will add my system & eGPU details or a build link to this my signature to give context to my posts

New Member
Joined: 1 year ago
Posts: 4
October 29, 2017 8:15 pm  

I never had to install any Thunderbolt drivers in Windows 10. The Akitio Thunder2 didn't come with drivers either.

mid-2011 21.5" iMac HD6750M + [email protected] (AKiTiO Thunder2) + macOS10.13 & Win10

Noble Member Admin
Joined: 2 years ago
Posts: 1815
November 28, 2017 9:54 am  

Upgraded to macOS10.13

From [APP] NVIDIA eGPU support for High Sierra (NVIDIAEGPUSupport)

Posted by: NayChan

Works PERFECT!!!!

Mid-2011 iMac with AMD dGPU and no iGPU. Akitio Thunder2 with EVGA 1050 ti SC 4GB.

  • Uninstalled goalque's automate-eGPU.sh script
  • Enabled SIP
  • Upgraded to High Sierra
  • Installed Nvidia Web Driver 378.
  • Disabled SIP
  • Installed NVDAEGPUSupport-v1
  • Logged In
  • Plugged in eGPU (System Info listed 'NVIDIA Chip Model')
  • Logged Out (The login screen briefly appeared on internal screen before fading in on both monitors)
  • Logged In
  • EVERYTHING WORKED!!!! Games, benchmarks, video editors and Photoshop.

SLEEP WORKS!! I've left it for 40 minutes and the system resumes just fine. The eGPU fans remain on and when it wakes up even kept my internal screen disabled via DisableMonitor.

RESTART WORKS!! The external monitor remains black but enabled until after login on the internal screen.

COLDBOOT WORKS!! In Sierra I would occasionally have to plug the eGPU in at the Apple Logo during boot. Now I can leave the eGPU plugged in all the time. The login screen spans both monitors during coldboot unlike when restarting.

NOTE: Do NOT try to enable SIP after you have eGPU working. The login screen will have a light blue background instead of the High Sierra wallpaper. It will still work if you login only once but with strange artifacts on the external monitor. Everything works but anything that is macOS system GUI like Finder and System Preferences will go bonkers if you drag the windows around. The Menu Bar and Desktop would also get ghosts of previous menus and windows. The internal screen remained just fine. If you logout and login again both screens will turn black with only the mouse displayed and allowed to go back and forth between them.

I tried everything to get it working again: every combination and permutation of hot plugging, booting, plugging in while logged in, plugged in at login, reinstalling Nvidia web drivers, enabling SIP with and without kexts, reinstalling NVDAEGPUSupport-v1, changing monitors, colors, refresh rates and more. Finally just reinstalled High Sierra fresh and repeated steps at beginning of post to achieve success again. This time I used the Nvidia Web Driver 378. since it was released by then.

Bootcamp and Windows 10 also work just as before only now with a curious quirk. In Sierra with goalque's automate-eGPU script I would just hold [option] at boot and select the Windows partition. Sometimes it would display black screens on both monitors and never continue booting. The rest of the time it would boot up on the internal screen and then enable the external monitor when ready for login. I would just restart until it recognized the eGPU. Now in High Sierra with yifanlu's app Windows absolutely refuses to recognize the eGPU at boot unless it is designated the Startup Volume. You can do this in System Preferences or by holding [option] at boot as normal and then holding [control] while selecting Bootcamp using the mouse. The up arrow below the boot volume will turn into a circular arrow. Doing this Windows recognizes the eGPU every time.

I never had sleep or cold boot working consistently in Sierra and am elated to finally be able to leave the Thunderbolt cable plugged in all the time. Works Perfect. yifanlu you are AWESOME!!!!


eGPU Setup 1.35    •    eGPU Port Bandwidth Reference Table    •    Several builds
2015 15" Dell Precision 7510 M1000M + macOS 10.14 & Win10