You can modify the inf for the latest XP drivers so that the 980ti works but AFAIK no one has gotten a 1080 to work. Rumour is that supposedly the earlier 10 model cards can be gotten to work but I doubt it and not much point if you want performance. If you want a newer card with a lower profile then may make sense.

Still using my 1080ti in my main desktop with my 980ti in my Q9650. Waiting for the release of the new graphics cards next year to see if worth buying, if so then I'll do some testing with the 1080ti with the Q9650.

With the 980ti on my Q9650 in Windows 10 Gears 5 runs at 30fps at 1920x1080, with D3D9 games in XP it's overkill but it works.

If I were you I'd put a XP compatible video card in there if you have enough room.

I currently am using a 780ti which is fine. I just wanted the better performance when running the Windows 10 boot. If I were to put both cards in there do you have a method for it automatically determining which card to use per OS? Hardware or otherwise? I don't want to use a switchbox if I can avoid it, I've already got mad switchboxes.

I just change it in the BIOS and run another cable to my KVM then have another keyboard and mouse plugged into the computer. Works for me when switching between
GPU 1: Zotac Geforce GTX 980 Ti 6GB AMP! Extreme GDDR5 ZT-90507-10B PCIe (Windows 2000 w/ extended kernel and above)
GPU 2: Quadro FX 1300 128MB PCI (Windows 2000 Vanilla and below)

Thanks for the info, maybe i'll just stick with the 780ti. I guess it would be fun to run an SLI setup that way possibly too.

If you want something more, buy Titan (Black or X), Black will work no problem (since it's 780 Ti with 6GB VRAM), and Titan X needs .inf addition to work.

Unless you re-write Windows XP driver side, to support Windows Vista/7 ones, Pascal on XP is just a dream.