Can I upgrade to Intel C2Q 8400 with DDR2-800 Ram?

E6300 runs 2 cores at 2.8Ghz not what you posted and the Q8400 4 cores @2.66Ghz.

It would help greatly if you posted what exact make your motherboard is as G31 is too general of a term.

Chances are it will work but on some brands it appears that you could run into issues with the Q8400 if you have all the DIMM sockets populated.

It would also not surprise me if such an upgrade necessitated a BIOS flash.

Posting your exact motherboard make and model would definitely help get you some better answers though.

The intel G31 Chipset motherboards usually support the newer processors... I don't think you will have an issue running the Q8400 but as posted above, it would be nice to have the motherboard specs just to be sure.

And no you do not need to upgrade your ram, DDR2-800 is perfect..

1333MHZ Ram is only with DDR3

G31 should support Q8400..
Ram will work just fine  

Thanks for all your advices. I've check the webpage of the motherboard manufacturer and it supports Q8400. I guess I can go ahead.

My E6300 is the old E6300 released in 2007 Q1 as Core 2 Duo. There's another new E6300 in the Pentium Dual Core family that was released one and a half year later. I have no idea how Intel could mess up everything by naming 2 different CPUs with 1 Processor number.

Stick with the 800