strange issue. im taking my gtx 950 from old PC and putting in the dell alienware R9, but get no display.
now the odd thing is, at one point i did get display but not anymore.
THe computer doesnt seem to fully power on as the led on the keoyboard remain solid, cant turn them on/off.
i have reasearch and researched but cant find anything. It seems its not realted to the whoel UEFi bios stuff as my PC is brand new, and is running uefi.
i even disabled secure boot. Still nothing.
there doesnt seem to be a uefi bios update or anything for the gtx950, the card is like 3 years old so it must be uefi compatible.
 
If i stick in the gtx1650 in the other pci slot, it seems to boot normally "most of the time" and at point i get display from both video card!!
its like it cant decide which card to use, race condition?
the dell power supply does have the 6pin poiwer connector which i plug into the card...
 
im lost, not even easy to explain whats the issue...please help..

Did you uninstall restart system than reinstall the NVIDIA driver? Edit: After that I would yet again restart system so the driver runs smoothly.

I am going to assume the GTX 1650 was an Dell OEM card but what about the GTX 950?

Here are the BIOS versions for your PC, from initial release (1.0.2) to the latest (1.0.7)..Update if needed, if not, try an older version..Make sure CSM (Compatibilty Support Module, that provides legacy BIOS compatibility by emulating a BIOS environment, allowing legacy operating systems and some option ROMs that do not support UEFI to still be used.) is enabled.

Yes the 1650 is the oem card. It also works fine multiple PCs. My GTX is retail, also works in mulitple pcs fine, excepp in my Dell R9. 
The computer is on the latest bios from Jan 2020. one thing to note is that the Pc has the new UEFI ONLY BIOS. It has no legacy/CSM bios option. i suspect thats where the issue is from. Perhaps the GTX950 cannot work in a UEFI ONLY PC.

I'd ask Dell support at this point, why their MB fails to work with that card

I suspect the Dell Alienware Aurora R9 may only except Dell hardware? Edit: Or Dell did not code in the BIOS such old hardware?
 
Out of curiosity for only the purpose of adding a story, why are you trying to put a four and a half year old GTX 950 in a less than a year old Aurora R9?
 
Edit2: "Ok so here is the reason. I need to use the Display port on the video card. Dells website says the r9 has the DP port. Every GTX 1650 card out there comes with HDMI and DP. However the one in my R9 DOES NOT have a DP port but instead a DVI! So yes, Dell is partially to blame, even though im not blaming them for my issue really.
Yes the R9 has an onboard DP port, but that is disabled as long as theres video card in the system.
My GTX 950 has 1 hdmi and 3DP ports. I am just trying to use that card in the R9 and the question is why it doesnt work, whereas that card works in every other PC i have. I cannot find anything anywhere that specfically states if this is realated to UEFI, Secure boot or the GTX950 not support UEFI(which supposedly it does, as do Nvidia cards as of series 5-6).
So my issue remains unfortunately."

It is a EVGA card after all.
Source: Aurora R9, GeForce GTX 950, no signal from monitor and keyboard