I have the very new Asus PB287Q 4K monitor and I've enabled display port 1.2 in its OSD menu system, but my Ubuntu 14.04 laptop still isn't using 3840x2160 at 60hz - it's stuck at 30hz. I'm curious what's the correct way to get this to 60hz?
I have an ATI Mobility FireGL M8900 and I'm using fglrx.
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Blackcomb [Radeon HD 6970M/6990M]
fglrx:
Installed: 2:13.350.1-0ubuntu2
Candidate: 2:13.350.1-0ubuntu2
Version table:
*** 2:13.350.1-0ubuntu2 0
500 http://us.archive.ubuntu.com/ubuntu/ trusty/restricted amd64 Packages
100 /var/lib/dpkg/status
Here is the relevant xrandr output:
DFP5 connected 3840x2160+1920+0 (normal left inverted right x axis y axis) 621mm x 341mm
3840x2160 30.0*+
2048x1536 30.0
Research indicates that for the Dell Precision M6600 laptop you may need the latest linux beta driver
Available here: http://support.amd.com/en-us/kb-articles/Pages/latest-linux-beta-driver.aspx (version 14.6 at this moment. Supports 12.04.4 and 14.04)
I realize this isn't a canonical answer but it may be helpful in your situation.
I believe that this answer already covers the vast majority of this type of question: How to see/change screen refresh rate or monitor frequency?
If this doesn't work I would contact Dell to discuss your warranty status.