GTX 980Ti not running at full speed after BIOS mod (Sierra 10.12.6)

[psycamel]

Hi

I recently flashed the BIOS of my GTX 980Ti to get a better performance in video editing and gaming.
I've flashed the BIOS using Maxwell Bios Tweaker under Windows 10 and managed to get a stable boost core clock @ 1507MHz (was 1241MHz) and memory clock @ 7800MHz (was 7000MHz).

After a successful flash and some benchmarks I've booted into my Sierra 10.12.6 (16G1815) hackintosh again to test the graphics card.
The 980Ti wasn't recognized at all, only "OSX Default Graphics Driver" were loaded. I selected "NVIDIA Web Driver" in the NVIDIA driver pref pane and was asked to restart the computer.
After restart, OSX default driver were loaded again. So I uninstalled the Webdriver and reinstalled it again (Version: 378.05.05.25f13).
That seemed to work. My graphics card is recognized again and working fine.

BUT: I've also made a benchmark in mac (Unigine heaven) and noticed in HWMonitor that the Memory Clock is going to 100% (7800MHz) but the Core Clock is only maxing at 1.24GHz - which is the original and unOCd boost clock of my 980Ti.

I am using SMBIOS MacPro 6,1.

Here are the screenshots of the settings I made in the Maxwell Bios Tweaker:
 

Spoiler

Screenshots

 

I really would love to get the extra boost for video editing on my hackintosh. Is there a way to achieve that?
Maybe there are still some old settings saved on the system somewhere...!?

Also I noticed that the 980Ti gets WAY hotter (I touched the PCB cooling plate) under Sierra than on Windows, that's why the fans (on windows they are off when not under load) turn on at some times.

Could it be that the card under Sierra needs more voltage or something like that to perform better?

I've also heard that original MacPros are underclocking the graphics cards because they would get too hot in their badly designed cases.

I would really appreciate it if someone could help me getting my card to work at full speed.


edit:// CUDA-Z is showing the 1507Mhz, but I am not sure if they are used. ...HWMonitor only shows a max of 1.24GHz.