This is going to sound stupid but Ive seen memery up to PC5400 but the maximum ive seen supported by motherboards is PC3200. How would use use the higher memery with motherboards?

Thanks

PC5400 is DDR2 memory and is packaged in a 240 pin DIMM module and isn't backward compatible with DDR motherboards. PC5400 most likely uses PC5300 chips but guarantees them to over clock to PC5400 speeds

PC3200 is DDR and is packaged in a 184 pin DIMM module