Just ran the AMD update. Have 3 5850's running clocked at 900/300 1088volts and have been getting 325Mh consistently. Now....all 3 cards are running under 250Mh.
WTF?
No need to roll back the whole driver. Run the uninstaller for Opencl only, then extract your old driver and install just the old file.
Only downside (of it is one) is that further uninstalls and updates may fail to remove the old cl SDK unless you keep the original installation file.
Was 11.12 the introduction of 2.6? So, I would just need to extra the SDK from the 11.11 drivers?
That is what I do, I actually run the ATI installer up to the point where it extracts the files, and then I cancel. On a completely driver-free system. I would then go to the device manager, find the video card, and then install the driver manually using the path C:\ATI\Support\11-12_vista32_win7_32_dd\Packages\Drivers\Display\W7_INF where they were extracted (or whichever version you want). That installs only the video card driver and no other stuff. Then browse your computer to C:\ATI\Support\11-6_vista32_win7_32_dd\Packages\Apps\OpenCL to install that driver's version of OpenCL. That's how you mix and match.
The ATI driver uninstaller leaves behind the newest OpenCL files, even when you choose "uninstall ALL ATI software". Follow these instructions before reinstalling:
https://bitcointalk.org/index.php?topic=54693.msg651989#msg651989