The CPC or Command or 1T and 2T. 2T will cost about 3-5% in real world performance. Benchmarks do not reflect the varation well and tend to misrepresent the difference as high about 30%.
1T is best if the RAM is stable.
BTW, CPC is not a timing persay like the CAS, RAS, ETC... it's a function of the memory controler.
Use 2T if you have stability issues. Most only use it when 4 RAM modules are being used or when the RAM is OCed at a high speed and require the stability of and/or a lesser divider or no divider at the desired speed.
Possible effect. (Just an example of possibilities.)Setting 2T to run stable with a 166MHz (333MHz) speed , vs a 133(266) @ 1T.