So, to conclude all this gibberish, I would suggest keeping CPC ON for better performance. But of course if you have a stubborn mule like my NF7, then by all means turn it off. It doesn't rely too much on FSB to regain the loss of performance and doesn't require your memory to be super overclockable. Furthermore, with most VDIMM options limited to a max of 2.9v, it would be a better choice to keep CPC ON because most memory will need more than 2.9v to overclock well. If you decide to do voltage mods, then the extra VDIMM can help the memory operate past its limits without losing performance.