intel core 2 quad q9600,ddr2 or3?



The processor supports DDR2 Ram because Lga775 sockets were not made when DDR3 came out
 
What RAM you have will depend on your motherboard. For most of LGA775's life, that was DDR2. Towards the end of that socket's lifespan, DDR3 RAM came out, and the last generation of boards, based on the P35 chipset I believe, did support DDR3. What CPU you have is actually irrelevant as back then the memory controller was on the motherboard, and not the CPU, so you'd have to look up your motherboard model and see what type of RAM it took.
 


P35 chipset supports DDR2 800 or DDR3 1066: - http://ark.intel.com/products/31916
P45 chipset supports DDR2 800 or DDR3 1066: - http://ark.intel.com/products/35133

X38 chipset supports DDR2 800 or DDR3 1333: - http://ark.intel.com/products/31919
X48 chipset supports DDR3 1333: - http://ark.intel.com/products/35143

The X48 was the last of the LGA775 chipsets.

Just FYI.

CT :sol: