I understand under certain circumstances a CPU and memory may need to be matched on speed to ensure there is not something like a 'wasted cycle' in waiting for a component to respond. I have heard of situations where memory or the CPU might waste every second cycle because the other component can't quite keep up with the requests. It seems like under-clocking one to match the other would be the logical step, but I also understand DDR memory runs on an internal refresh cycle to continuously rewrite the memory contents. This cycle is likely unchangeable, thus potentially a mechanism for this 'wasted cycle'.
I have acquired an Intel XEON CPU that is rated to run with at best 2166 MHz RAM, yet when searching, this exact speed of RAM is more expensive than its faster equivalent part.
Might I actually expect a performance hit when using this faster memory?