Run the test yourself! Download a number crunching application like Super Pi and run the 1M digits test. Set the CPU core speed to the factory number and compare the Super Pi time between 100MHz, 166MHz, and 200MHz RAM speed. Going from 200MHz to 166MHz will cost you at least 80MHz core speed with the AMD platform. However, most users will DEFINITELY benefit by dropping to 5:6 memory divider and running the RAM at 220MHz.