i'm planning on buying a used macbook pro 13 inch late 2011, but have a question. it's quite cheap because it has only 4GB of ram. now, i have ddr3 sodimm memory spare, but it's 1600mhz. on apple's page it specifies that this model uses 1333 mhz memory. will it work with my spare ram? just at lower clock speed? or will it not boot and would i have to get new memory for it? thanks!