Actually, Cool N Quiet is the idle state, C1 allows the cpu to essentially shut off unused cores, C1E is AMD's additional feature that puts the entire cpu in sleep mode if all cores are in C1 mode.
For overclocking, disable C6.
C6 is the mid-clock state and is the cause of frequency bouncing, it does this to reduce power consumption and heat, but if your overclocking, it attemps to compensate by slowing it back down.
I run my 8120 at 4.7 ghz and only disabled C6. If you disable CnQ and C1, C6, ect., your cpu will run full speed all the time. I would only recommend during the testing phase so you know what your temps will be, unless you want a high power bill when the computer is just on and doing nothing.
Thanks, very helpful. So, for a Phenom II X6 1090T that I will be overclocking a bit, should I disable C6 (if I can find where to do it) and leave C1E and C&Q enabled then?