Adding another 2 GB to my 2011 13' Macbook Pro

I just recently bought another 4 GB of memory for my late 2011 13' Macbook pro and i thought i read somewhere that if i mix a 2GB and a 4GB instead of a 2GB and 2GB or 4GB and 4GB, it will effect performance. Is that true or does it not matter if i mix the amount of GB's?

Thanks

Memory modules should always be installed as matched pairs. However, I don't think it's going to make a noticeable difference. You can always order another 4 GB module and install 8 GB instead of 6 GB.

okay, i think ill just buy another 4GB one just to be sure. Does it matter if they are 2 different pairs? the first one i bought is a samsung and i was thinking about buying a Other World Computing one for the second 4GB cause its about 5 bucks cheaper.

Thanks

That can be tricky. I've had both good and bad luck mixing manufacturers. If possible, try to stick with the same exact module from Samsung. Or if you can, get a refund on the Samsung module, and then order a matched pair from OWC. I buy all my memory from OWC and highly recommend them for updating your Mac with memory or hard drives.

You take a chance with incompatibility by using 2 different brands. Having mismatched sizes means dual channel is not enabled, given the price of RAM no reason not to have 8GB.