Note: this post is just a note, for anyone to check out, or discard. It is not intended to be a guide on how to get GPU working, since it does not work, for reasons described later.
If you want to play around with GPU drivers on let’s say a Lumia 950 XL, you will need the widely available driver pack (which you can find on Proto Beta Test as well).
The Operating System version on the phone must be at the very maximum, 17134, no newer Operating System version will work, and may damage your display.
Inside the driver pack there’s an experimental folder, with drivers for display and GPU. On a 950 XL, you need to install OEMPanel for the 950 XL (not hapanero), you also need the hdmidpi driver. The hdmidpi driver is an issue however, since we do not have the driver for this device, we install a dummy kmdf one, known drivers available are kmdffake (by ADeltaX) or you can also use LumiaNull
You will also need to install the GPU drivers, to do this, locate the qcdx8994 folder inside the experimental driver pack. Now install all drivers we just mentioned at once.
It is important to note you must batch install all drivers at once, otherwise you may get blackscreen issues.
Once done, you can reboot or boot your device up. You will see a black screen on the device after the windows logo, and probably nothing after.
Why does this happen? Currently we’re facing an issue where the driver reports one DirectX feature is not supported by the GPU, which prevents DWM from working correctly.
You can however disable DWM (which will break winlogon, so you may want to use auditmode (HKLM/System/Setup/SetupType=1))