iMAC 5K el capitan + Sonnet III + GTX 970 Boot Problem

[Proph]

Hi, I have a problem with booting my iMAC 5k (late 2015, i7, 27") when using Sonnet lll + GTX 970. 

After clean install of 10.11.3 el capitan I disable System Integrity Protection, download newest CUDA, plug in my Sonnet lll with GTX 970 installed and run automate-e-GPU (https://github.com/goalque/automate-eGPU ). I activate -a mode of the script and restart. First restart works fine, GTX 970 works but after another restart  my imac gets stuck while booting with black screen. I know thats a common issue with eGPU but I tried all fixes I found, nothing helps.

 

One thing that works is the power up process described here (https://www.techinferno.com/index.php?/articles/guides/2015-13-macbook-pro-gtx97016gbps-tb2akitio-thunder2-win81osx1010-tranj10-r2/)

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Power up process:

This is the power up process I always use to consistently have a successful boot without any black screen issues.

1) Have everything powered off

2) Connect thunderbolt cable to eGPU and MacBook

3) Power on the eGPU power supply (use a power strip with on/off switch)

4) Wait ~15 seconds

5) Power on the MacBook while holding option key

6a) Select the boot partition you want

6b) If you run into a blank black screen:

- Force power off for MacBook

- Power off eGPU power supply

- Disconnect thunderbolt cable from MacBook

- Power on the MacBook while holding option key

- Boot into OS X, log in, and shut down

- Go back to step 1 (there will be no black screen issues for at least the next boot up)

- If you still are getting black screens after repeated tries then try a NVRAM clear (https://support.apple.com/en-us/HT204063)

- Note that the NVRAM clear does mess with the changes implemneted by automate-eGPU. So you'll need to run 'sudo ~/Desktop/automate-eGPU.sh -skipdriver' to re-enable the changes

- If the NVRAM clear doesn't help then try enabling -a mode with automate-eGPU by running 'sudo ~/Desktop/automate-eGPU.sh -a'

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That process works one time but I dont want do do that whole process every time i start my imac

Tried the NVRAM clear and automate mode of the script restart- stuck in black screen

Also tried to make a backup of AppleGraphicControl.kext and replacing the backup after running the script, imac wont boot at all even without eGPU plugged in.

 

When i boot without eGPU - no problem, when i plug in the TB connection after I booted, the GTX 970 is called Nvidia Chip Model, so that dont works neither.

 

I just need the eGPU for CUDA, no video output from the GTX970 is needed.

Can anyone help me? I would donate some cash for a working solution.

 

Best Regards, Proph