Got an new HP EliteBook 840 I7-3600U, Intel HD 4400, 8GB Ram and a new HP Z30i monitor with resolution 2560x1600 60Hz.
I got problems with the monitor Z30i, it goes down in Power save mode when ill connect it to the laptop whit DP. I have tryed DP to DP and DP to DVI cabels nothing works. I have tryed Intel driver 10.18.10.3345 and the one form Microsoft update 10.18.10.3379. I have tryed both Windows 8 64Bit and 8.1 64Bit
I got 2560x1600 one time when i tryed a more powerful AC adapter with Windows 8 64Bit and then i reinstalled to Windows 8.1 and the monitor went down in Power save mode
AC Adapter Model: HSTNN-LA12
INPUT: 100-240V~ 3.5A, 50-60Hz
OUTPUT: 19.5V 11.8A 230W
My 4 years old IBM x201 with Intel HD Graphics works fine with the Z30i monitor on DP to DP cable