2560 x 1440 on Gt 240 via HDMI

[nefroone]

Hi guys,
I recently upgrade my monitor with a dell u2715h.
The max resolution aviable in El Capitan is 2048 x 1152 on HDMI, wich is better than before but not the best...
I know that gt240 can handle 2560 x 1440 @60. The only way to do it is to force resolution with switchresx, but i can obtain only 40 Hz maximum, that is not so good...
How can i obtain full res of 2560 x 1440 @60?
1) is this a cable problem? can i try a better hdmi cable or a dvi-dp cabel?
2) is this a hardware problem? must i upgrade my graphic card?
3) is this a driver/software problem?

thanks in advance.

 

[Algos]

If you want 2560x1440 to just work you need to use DisplayPort.

If you search the forums for "2560x1440 HDMI" there's threads with solutions.

 

[slim.jim]

You can give the pixel clock patch a try: https://github.com/Floris497/mac-pixel-clock-patch-V2

 

[Guancho]

I solved the same problem with a Dell u2515h by using a dvi-to-hdmi cable. With this, I get the full resolution.