@mogresh: Windows 8 is not currently a supported Operating System.
This could be an issue with the 12.6/8.98 version AMD drivers or you may just need a clean reinstallation of your current drivers. We have found the most stable AMD drivers to be 12.1/8.93
Please do the following: Uninstall video driver, clean boot and then clean driver install.
ATI recommend removing drivers via their own catalyst:
1) Click on Start
2) Open the Control Panel
3) Select Programs and Features
4) Select ATI Catalyst Install Manager
5) Click on Change
Instructions on performing a clean boot: http://support.microsoft.com/kb/929135
When installing AMD drivers, just perform the installation as normal after the clean boot.
Please post again to let us know if this increases your game performance.
Thank you for playing Star Wars: The Old Republic
There have been massive driver improvements since then.