Klem

Hi! Ok. Check your PM box.

Hi! Yes of course. Check PM.

If you want to keep the Fast Boot option to enable always after restart, just flash this: BIOS.rar

I think that it's a custom vbios.

Just download it, and then flash it.

Ok. If you search on Techpowerup, then you can find this link: https://www.techpowerup.com/vgabios/170181/170181

Hi! Post here your stock vBIOS.

Hi! Ok. Check your PM box.

Hi! I also don't know if the non g-sync GTX 980m working on a P750DM-G. Sorry.

It's not true. Dell officially supported GTX 765M.

Hi! What the model laptop?

Ok. Try this. 2.rom

Done. Try.

Yes.

Try to do all steps, but skip disconnect the CMOS battery.

As first step you need to remove back cover, disconnect Power Adapter, disconnect Battery, and CMOS battery, unplug all RAM modules. Then do Power Flee by pressing power button 20 secs or so. Then connect AC, Power on, it will bootloop cos no ram installed. - in one of the shutdown in-between bootloop , quickly connect CMOS battery connector back in its place. Let it reboot, - it will shutdown again cos still no ram installed, - after another shutdown ( still in-between bootloop ) quickly connect/insert 1 ram modules to its placed. Then after next reboot it should back to life to enter Setup Mode. Then you could load Default Settings and restart or shutdown to connect battery and another ram modules, if you had 2 slots installed.

Strange. You wrote before:

Hi! Check PM.

Hi! Post here your screenshot in NVIDIA Inspector.

Hi! Check PM.

Hi! Send me your stock vbios, or upload it to any fileserver and send me the link.

Hi! Send me your stock vBIOS.

Hi! Ok. Check PM.

Your gtx 980m from Clevo or from MSI?

You can try to use this solution: https://community.dell.com/thread/6037