Series Acer Aspire 5349/ Aspire 5749 / Aspire 5749Z Are the NTBs the same (they differ from the installed CPU from the factory) They have a CPU in the G2 socket. It is therefore possible to install a Sandy Bridge CPU for socket G2. Max CPU by performance class: Celeron B840, Pentium B980, Core i3-2370M, Core i5-2540M, Core i7-2640M, Core i7-2960XM. BUT I RECOMMEND TO OBSERVE TPD 35W for CPU considering the cooling performance. Therefore, the "most powerful" is the Core i7-2640M. And one more note. Acer recommended 8GB of RAM for these notebooks, but all CPUs and motherboard chipsets support 16GB of RAM. If you have the original CPU or a CPU upgrade, you can fit DDR3 SODIMM 2 x 8GB RAM and you have 16GB RAM.