Intel CPUs run internal clocks of 1600MHz, so for a best performance to heat ratio a 1:1 is best, therefore 1600MHz ram suits Intel CPUs like a champ. AMD uses 1866 better, except for the APUs which use system ram for the gpu, and depending on the APU can benefit with up to 2133MHZ ram. This is not to say these are the limits, but once you pass the 1:1, you start making the CPU work harder to keep up with the data inflow from the ram. Any time the CPU has to work harder, it creates heat, so without a good cooling solution, idle temps will go up as will load temps. This makes 1600MHz a good all around ram solution, so manufacturers are in more competition, so lower prices.