R9 280X Resolution Problem -NO 2560x1440 under Yosemite

[Geierwally]

I have a problem with the resolution of my video card.
When I boot, then I have the full 2560x1440 resolution.
Once the PC is on Login Screen, the resolution drops to 1920x1080.
I've tried everything but nothing has helped yet.


Graphics card is a Sapphire Vapor-X R9 280X, Model: 11221-20-40G. It has 4 ports: DVI-D, DVI-S, HDMI and 1 x DisplayPort (no mini DP). Monitor is Acer K272HUL. However, only the DVI-D port is working under Yosemite. On Post and boot logo they're working all.


Here is a video of my problem: https://www.youtube.com/watch?v=B3DWuKJgXrA




The card worked OOB. BruceX takes 28 seconds and Luxmark is 2330. So I think the card is working. Only problem is the small resolution
Can anybody help me?


Many thanks!


Alex

 

[Stork]

Open the Systems Preferences > Displays.

Option Click on the Scaled button to see all resolutions.



Reference
https://support.apple.com/en-us/HT202532

 

[Geierwally]

Thank you for you reply but I've already done this. Max choosable resolution is 1920x1080 under scaled menu.

 

[Geierwally]

Problem solved!

I switched the Framebuffer from Futomaki to Hamachi.

sudo nvram 1F8E0C02-58A9-4E34-AE22-2B63745FA101:AtiFramebuffer=Hamachi