How do you know what kind of PC3 memory your MB uses?

DDR3 memory. List your motherboard and processor and I'll recommend some.

@zipzoom Im sure it does, but not when your ordering online, newegg does not mention what type of DDR3 memory the MB's use

im getting the ASUS P6T Deluxe V2, was gonna get the OCZ Platinum (3x2) but i dont know what the (PC3 *12800*) part specifies, is it like a part number to the proper MB, like only motherboards that support the 12800 memory, or is it memory speed?

It's a different way of saying the same thing. For instance, DDR2 800 is the same thing as PC2 6400.

There are very few recorded compatibility issues with the i7 controller. As long as the DDR3 operates at a voltage that does not go over 1.65V, you should be fine. OCZ Platinum is a good choice.

ty proximon, how exactly do you calculate the PC2 number, if i may ask?

Oh nvm, multiply by 8 lol