[mzso]

Originally Posted by chros

That's correct.


Oh, sh*t It's even older than mine (prev gen Fermi), but: it's a desktop GPU!
You can try out these ones as well for 4k hdr content, along with the "scale chroma seperately" setting:
- enable 1 more in trade performance: the 1 below "scale chroma seperately" setting (maybe it's called gamut mapping)
-- this one will screw up the colors, but it helps performance
- disable "highlight recovery" in hdr menu under your display (it's really taxing otherwise)
- enable crop black bars: that will help with wide-screen content a lot (but not with fullscreen ones)
- dithering: ordered

I think this time you should be able to use at least bicubic scalers for both luma and chroma.
If it's working then try to disable the above set gamut mapping setting in trade performance and see what happens.

Thanks for the tips.