Well upgrading RAM can be tricky. If I am not mistaken, those CPUs take DDR3 (you want to research your exact model before making decisions). Also, it depends on the speed as well (1866,2133, etc). I generally getting a set, that you know there is no mistake. You can try to use a another 4GB, but if it is slower than the one you have, the overall system will perform at whatever speed is slower. Think "you are only as strong as your weakest link."