I would raise this issue through "Issue reporting form, but my card "R9 270x" and driver version (13-11) is not yet available in the dropdown list.
ASUS Radeon R9270X-DC2T-2GD5. Not overclocked.
AMD Catalyst Driver Version, and Driver History:
13-11 beta 1
Windows 7 x64 Sp1
In desktop (in 2D mode actually, I am using aero in windows 7), the graphic card doesn't go to the lowest power trim, when monitor refresh rate in the driver is set to 144Hz. Here are the settings the card runs, when refresh rate is set to 144Hz - GPU clock: 450MHz, Memory clock 1400MHz, GPU vcore 0,95v.
When I set refresh rate in the driver to 120Hz and lower, the graphic card can use lowest available power trim which is - GPU clock: 300MHz, Memory clock 150MHz, GPU vcore 0,875v.
It is very easy to reproduce. It works like that every time.
I used GPU-z to check GPU clocks, RAM clocks, GPU vcore.
Motherboard or System Make & Model:
Asus Maximus VI Hero
Display Device(s) and Connection(s) Used:
Asus VG278HE (144Hz refresh rate) connected to the card using Dual Link DVI cable.
Intel Core i7 4770K not overclocked.
Motherboard BIOS Version:
Asus Bios version 0804 x64
System Memory Type & Amount:
G.SKILL RipjawsX DDR3 2x8GB 2133MHz CL9
I hope, this will be fixed in future versions of the drives.