Does 4x4 ram or 2x8 ram perform better

why are you talking about cores? cores & ram just dont make any sense. If you want 8gb ram, you need to look at how many ram slots you have. If you have 2 more slots, you can add 2 modules of whatever you want, speed of ram hasnt got anything to do with the size of the modules. Ram is rated in speed though, Mhz and latency are the 2 main factors. Running ram in pairs also allows it to run faster as it can read from 2 pairs at once. Dont go to an apple store, a knowledgeable PC hardware place should be able to upgrade the ram and wont charge you through the nose like an Apple store. Apple computers use the same ram as any windows PC. Whatever speed the ram runs at will be limited to whatever the slowest part is. So if you intend to keep the ram you have installed, whatever ram you get should be rated the same Mhz or faster. Faster ram honestly wont make a noticeable difference for what you are doing.

What i7 Quad core? If it is a socket 1366, you will want your ram in multiples of 3 (3, 6, 12, etc.) If it is a 1156/1155, you want it in twos (like you have it listed). you want as few sticks as possible that will a) fill all two or three memory channels and b) give you the desired ram quantity. Filling all 4 or 6 slots is fine too (especially when adding ram to an existing system), as the only downside is that is runs the memory controller harder and thus you must use looser timings or lower speed (however at stock settings, which I assume you are running at, this is not an issue).

I think he is talking about the RAM sticks and the size per stick.

If anything you always want to get matching pairs for the best stability. As well you want to look at the timings and speed. Depending on which Core i7 (if its an earlier one on LGA1156 or newer LGA1155 part) is what the top rate speed the mobo can handle. LGA1156 I believe was set for a top end of 1600MHz DDR3 while LGA1155 is DDR3 2133MHz.

With the channels, the furthest slots away always have lower performance so you want to use the closest ones. I would say go for 2x4GB like these:

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

A bit pricy, well actually thats about what I paid for 4GB 4 years ago so its not that bad really.....

Best answer selected by MikeTheDimmer.

Several best answers, but your answer kept me in the 2x4gb or 4x4gb configuration. I didn't need to go 2x8gb and create newer issues. Also, am able to upgrade at later date to 4x4gb, if the software demands it.

As far as processor, I have 065-9512 2.93ghz. memory 065-9451.

Does that help on specs?

Soooo, You have a mac laptop? That would explain why you went to the Apple Mac store. Makes sense now. That number seems to coincide with the i7 740QM, (Quad Mobile), and the memory is DDR3 1333MHz. Those numbers helped a little but if you have a laptop you most likely have only 2 memory slots. Have you taken the back off to see? And if so look at the numbers on them and see/write them back here just to be sure. Here is a link to newegg for some 2 X 4GB laptop memory kits. Check them closely to make sure they are 2 X 4 - as you go down the 1 page list they start turning into single 4 GB sticks, (that you can buy 2 of instead of a kit), and then 2 X 2 GB kits. You can GO HERE and Crucial will scan your machine for you and then make recommendations based on that.

If it is a mac then you might want to check back with your apple store. They might have something on hand that's comparable in price and will/should install it at no extra charge. Also, It probably doesn't matter since it all seems to be 1.5v, 204 pin, 9 CAS latency laptop memory but make sure it is mac compatible. I've never worked on them so I'm not sure if it is the same. My guess would be yes but it's just a guess.

And if it's not a mac then the supplied list will work.

Sorry for all the guesswork but if you give us a list of the name brand, make and model# of the laptop or desktop as well as a service tag number or serial number we could get more specifics and most likely narrow it down a bit more. But given what we have so far it should answer your immediate questions.