I have a Dell 8300 from mid 2003, it came with 2 256MB PC3200 chips(400Mhz) I bought two 512Mb chips PC3200 (400Mhz) from a different company. When only one pair is in it works at full speed, but when i put both pair in it works at 333 Mhz, I know i'm putting them in the right spots because it would switch to single channel if i didn't. whats the problem?