2560x1440 resolution no longer available on external display

Hi

What worked for me was this.

I bought a Thunderbolt/Mini Displayport to Displayport cable v1.2 (4k compatible)

I also used the http://embdev.net/topic/284710 but i'm not sure it was even necessary

in my situation.

I'm on the latest Sierra 10.12.3 so maybe it is fixed now.

But everything looks fine now on my Dell U2723HM and Macbook Pro 15" Retina.

Hope this helps. I was also in the same situation as everybody else with only Full HD

resolution but now i have 2560x1440 and it looks great.

Hi JBJ73,

the same was just happening to me, and after some hard research I ended up finding this. Looks like Mavericks has some trouble with the default EDID config of some displays.

Down the page you will find a ruby script that suposedly generates an EDID file adequate to any display, but that ended up not working for me either.

I was able to get my U2711 full resolution through displayport by using the first file linked by the OP (I know it's suposedly for other Dell displays, but trust me, it has worked for my U2711).

You should decompress the zip, and it will create a folder named U2713H_U2713HM_Mac_EDID_override. Get inside that folder using Terminal, and then copy the folder it contains into /System/Library/Displays/Overrides using the following command:

sudo cp DisplayVendorID-10ac /System/Library/Displays/Overrides

(You need to use sudo because you are copying the files to a folder owned by root)

Hope this helps!

While inside System Preferences > Displays | Hold the option key > Detect Displays if still doesn't work after PRAM reset from here: http://support.apple.com/kb/HT1379

Not sure if you know this but when you PRAM make sure the adator is NOT connected, reconnect once you back on the Desktop.

Can you provide the brand model of your adaptor?

Glad that work around did it for you thanks for the update.

Try this;

Hold the Option button when clicking on Scaled, see if the correct resolution now becomes avaliable.

Thank you actionmaker, that is the solution! I had exactly the same problem. I also have same Dell display as jbj73 has.

I have two ASUS PB278 which I connected with HDMI originally (1080p was best option), and switched to a mini-display port to display port connection, and resetting the PRAM worked for me! Thanks!

One thing to note is after I restarted and reset the PRAM, even though I could select 2560x1440, I had to also turn the monitors off then back on (they had some artifact lines being drawn before doing this).

I wasn't getting HiDPi modes shown in the display preference and holding down Option key worked. Thank you!