Yesterday I purchased a Dell U2713HM a 27″ display that gives me up to 2560×1440 resolution.
I connected it with an HDMI cable to my Retina MacBook Pro 15″ (late 2013). At first it didn’t work as expected, and I was getting “only” full HD resolution, I knew this was a possibility because I was not using the correct cable. You need a Mini Displayport to Displayport to get the full possible resolution, I purchased the cable but didn’t arrive yet.
Today the cable arrived so I plugged the new screen to my Mac, and surprise! It didn’t work either. 🙁
I was getting a strange resolution, and then I was able to get full HD again, the most, but not the full juice.
I started reading online and found a lot of suggestions, unplug, restart, reset SMC and more. I realized my laptop was almost new, and I could call Apple support. So I did, but unfortunately Daniel, the support representative was as lost as me. While he put me on hold (he was asking somebody else), I found the solution online.
It seems the EDID (Extended Display Identification Data) in Mavericks was not right for my new monitor (I also read this solves the problem for other Dell Models U2711 & U2713H). Fortunately, from this link (I also made a mirror here just in case) I could download a ZIP file which contains the correct EDID for these Dell monitors.
I just download the file, and uncompress it. Then copy the folder to the following path: /System/Library/Displays/Overrides. Then restarted and the display will work as it should have the first time, full 2560×1440 no problems!
Note: In my case, I got a bad start first, and then the computer started correctly so everything was ok. I’ve noticed it took a couple more seconds than what a normal reboot would take.
Just when OS X was restarting, Daniel (the Apple supporter) came back to me. I explained him what I just did and he was surprised of the solution. I gave him the information and he told me that he will report it so the engineering team can prepare an update for Mavericks.
For the time being, you have the tip here, hope this can solve your problem the same way it did for me. Now, I am enjoying full resolution on my 27″Dell screen :).