Same here: R9 280X, performance of OpenGL games (Minecraft and Half-Life) is highly unsatisfactory. Tried drivers 13.9, 13.11b4, 13.11b5, and 13.12.
Looks like that version 13.1 of atioglxx.dll didn't work for me Tried it in the game directory and in SysWOW64.
My explanation of what happens
I've noticed that Half-Life (hl.exe) loads aticfx32.dll, and Minecraft (javaw.exe) loads aticfx64.dll. Not seen either use atioglxx.dll through Process Explorer. Those two DLL's I just mentioned are for DirectX 11. I'll do some more digging to see which DLL's are involved.
32-bit apps --
atiadlxy.dll: ADL Component
aticfx32.dll: AMD Inc. Radeon DirectX 11 Driver
atiglpxx.dll: Advanced Micro Devices, Inc PowerXpress Vista OpenGL Driver
atigktxx.dll: Advanced Micro Devices, Inc PowerXpress Vista OpenGL (thunk) Driver
atioglxx.dll: AMD OpenGL driver
64-bit apps --
atiadlxx.dll: ADL component
aticfx64.dll: AMD Inc. Radeon DirectX 11 Driver
atig6pxx.dll: Advanced Micro Devices, Inc PowerXpress Vista OpenGL Driver
atig6txx.dll: Advanced Micro Devices, Inc PowerXpress Vista OpenGL (thunk) Driver
atio6axx.dll: AMD OpenGL driver
Looks like there are 3 driver DLL's that might need downgrading to 13.1. You will of course need to obtain the correct 32-bit/64-bit image types for these files. If you're running 64-bit Windows be sure to put the 64-bit drivers in "system32" and 32-bit DLL's in "SysWOW64".
Edit2: All 3 of those files in their older 13.1 version didn't help resolve OpenGL performance. Checked with Process Explorer to ensure old versions were being used.
10:47 AM by