I know this sounds like a silly question, but I am buiding a PC for my sister and am going with the i5-9400f. I ordered a DDR-2400 RAM kit to go along with it assuming it would work fine. I just checked Intel's site however, and it shows the only compatible ram speed is DDR4 2666? I thought the base speed of DDR4 was like 2133, Why would it say only compatible with DDR4 2666, that makes no sense that this processor would only be compatible with one particular OC speed of DDR4. If it were only compatible with one speed, it would be the base speed, like 2133 right? Can anyone confirm this? Will the I5 9400f work with DDR4 2400, or should I just return it and get DDR4 2666? I got a pretty good deal on the RAM, its corsair LPX c14.