(In reply to Robert from comment #12)
> At least I now know that I can't do anything further. It just would be cool
> if one of the AMD engineers could confirm my assumption that with a
> resolution of 5144x1440 the card always runs at highest memory clock speed
> as it does with a multi monitor setup (from what I've read so far).

[Note, I'm not an AMD engineer.]

In some monitors, such high modes are actually exposed by presenting multiple
"tiles" as separate screens. As far as the GPU is concerned, it's 2 actual
monitors (this can only work with DisplayPort, of course).

Can you check if this is the case? I believe "xrandr" should report 2 separate
monitors in this situation. You mention you have a 49WL95C-W, which the
internet suggests is indeed just 2 panels placed next to each other in a nice
plastic case.

And in such cases, I believe the AMD drivers clock to the highest rate, since
reclocks will cause flickering (since the vsync's of the 2 monitors aren't
sync'd to one another).