I have the same problem... Can 11.11 works well on win8 64bit?
This is your GPU returning invalid hashes from it's kernel. This is because new drivers are crap for older cards.
- Uninstall AMD APP SDK
- Uninstall AMD Catalyst Install manager: choose "uninstall all software", make sure you have only a VGA driver after restart.
- Manually remove these files not removed by the installer; any other obvious ATI files with the same file date:
C:\Windows\System32\amdocl64.dll
C:\Windows\System32\amdoclcl64.dll
C:\Windows\System32\OpenCL.dll
C:\Windows\SysWOW64\amdocl.dll
C:\Windows\SysWOW64\amdoclcl.dll
C:\Windows\SysWOW64\OpenCL.dll
- Install just the Catalyst 11.11 driver package (no SDK is needed; the AMD APP runtime is included with driver)
- Mine just a bit slower on your 6870 than a 5830 would.
Better:
- use cgminer
- set phatk worksize to 256 and underclock GPU RAM to 300MHz for best power efficiency and higher hashrate