I want to add 2x4GB DIMMS to my 2011 iMac with the standard 2x2GB DIMMS for a total of 12 GBs of memory. Does it matter which slots hold the 4GB DIMMS and which slots hold the 2GB DIMMS? For example, should I put the 4GB in the first two slots and move the 2GB DIMMS to the last two slots or just add the 4GB DIMMS to the last 2 slots and leave the 2GB DIMMS where they are.