4gb ram, only one slot

Question

I have 2gb ram in my macbook and bought another 2 gb ram card and went to put it in and it looked like i could only fit one card in my mac. So, do i have to buy one card that is 4gb insead of 2 cards of 2gb to equal to 4 gb? 'cause i don't see how i can fit another card, it looks like i can only fit one card

Answer 1

GfulDedFan wrote:
If you have the Aluminum MacBook, the second slot is underneath the visible first slot. In other words, the slots are stacked instead of side by side as in the White/Black MacBooks. Please see [*this video*|http://eshop.macsales.com/installvideos/macbook13_unibody_memm>.
You currently have 2 x 1GB modules installed. In order to upgrade to 4GB, you will need to purchase a 4GB kit (2 x 2GB). You could purchase 1 each 4GB module instead and install only one module but the 2 x 2GB would be more economical and give you better performance from using a matched pair. -GDF
I'm not sure if it's the case that 2x2GB as a matched pair would give better performance than 1x4GB. It's kind of complicated, but I'd think everything that's done when switching between 2 modules in matched pairs can be done with the internal "bank switching" that's done in the large memory module. If anything, I'd think 1x4GB might be faster.
Of course I'm basing my belief on my reading of Intel's description of their memory controller. NVIDIA could very well be doing it as true "matched pair" operation where the access is done in parallel with an effectively double-width data bus. I doubt it though. Most of the benchmarks I've seen seem to indicate that the most important factor for performance is having more total memory. If you could effectively double your data bus width with matched modules, I'd expect that there would be substantially faster performance from 2x2GB compared to 2GB+4GB.
http://eshop.macsales.com/Reviews/Framework.cfm?page=/Benchmarks/6gb_tests.html