Custom Resolution not compatible with monitor?

[Laurits76]

I have a ASUS MG248Q 24 inches the resolution is 1920x1080, and it is 144 hz.
I have the amd graphics the R9 270x Dual x Saphire.
i use Displayport that is supporting my 144 hz.
and when i try to set a custom resulution in amd crimson, (the resolution is 1440x1080.)
it says that my monitor isn't compatible?? like wtf why shouldnt it be??

 

[TechyInAZ]

First off, why would you want to set a weird resolution of 1440x1080?

Custom resolutions aren't always supported, it's always a gamble.

 

[Glenwing]

Is GPU scaling on?