This is a super question. I also am interested in upgrading my PC via new cpu. I will add this post to try to get a busy Intel person to take note. My mobo manufacturer says my mobo only supports up to E4500, with LGA775. The E4600 cpu has LGA775. The E4700 has PLGA775. So, I think maybe these little tiny differences are details...and the devil is in the details! I think maybe safe course to avoid wasting money is to go with every tiny detail...e.g., LGA775 is NOT same as PLGA775.