“The usual suspects declined to disassemble one of the "Mid-2010" iMac models -- the iMac "Core i3" 3.06 21.5", "Core i3" 3.2 21.5", "Core i3" 3.2 27" and "Core i5" 2.8 27" -- but Intel provides information on the default mounting for the processors these Macs use.
Specifically, Intel reports that the applicable Core i3 processors eachsupport an FCLGA 1156 socket and the applicable Core i5 processor supports an LGA 1156 socket. It isn't entirely clear how, or if, the FCLGA 1156 socket that the Core i3 supports is different from the LGA 1156 socket that the Core i5 supports, but it is believed that the sockets are the same and just the Core i3 "package" is different.”