What crimson edition do you have?You could roll back to the previous driver version.
Crimson is now GPU only.
Your CPU will have power management like C6 C1e C&Q, that all reduce power when the CPU is idle. CPUs are idle most of their lives. Enable in your BIOS.
You can change CPU power plans and CPU usage in Windows Power Options...
Set Power Saver to Max 10% or something. Then switch when you play a game. If this is what your after. You could use this for easy switching once you have the plans setup.
Hope this clears things up.