I've just bought my first iMac, the 5K retina and love it. I bought it with 8GB of memory with a view to upgrading the memory myself to save a few pennies. I read it takes DDR3 1600Mhz memory which is the same type I have in my Lenovo W540. Does this mean I will be able to take the memory out of my W540 and put it in the iMac safely, or is there something else in the specifications which would make it incompatible? As you can tell I'm not very clued up on computer memory. Thanks in advance.