I know usually it's better to run the memory on dual channel, if possible, with a Kit of 2x2GB, but at the moment my laptop has 2x1gb and I wanted to upgrade it.

Which means, I can either buy a kit of 2x2gb and try to sell the 2x1gb I already have, since the laptop only has 2 slots, or I can buy 1x4gb (also a bit more expensive) and add keep one of the 1gb dimms, making it 5gb non dual channel.

From what I hear, dual channel only gives you performance increase of 3-5%, so I'm unsure of which option to pick.

  • Funny how my question was edited to remove the "hi" and "thank you" :P – Andre Sep 4 '10 at 18:05
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    SU is pure Q&A, not a forum. Salutations and signatures are discouraged, we try and keep the questions short and to the point and on topic. :) – BinaryMisfit Sep 4 '10 at 18:10

From what I remember from the upgrades at work recently, the MacBook Pro's will only run in pair combination of the same memory types and sizes. Therefore the only recommended and supported configuration is 2X2GB = 4GB.

The few we did try and mix memory in did not even boot. However, I am not saying that this hasn't been done, and there is the odd chance that it will work. In the older model MacBook which I own the bigger modules were not supported. Ie. 2GB + 1GB would not work together at all.

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    Thanks, I was thinking of going with the 2x2gb because its £30 cheaper, so I guess I'll play it safe :) – Andre Sep 4 '10 at 17:53

I'd say go with more RAM.

The question is a bit more complicated that that. The core is: Are 5 GiB of RAM going to be enough? If you plan to use this laptop for a long time, it would be cheaper in the long run to get 4 GiB and sell 1 GiB. After few years, you could do same thing again in case you start running out of RAM.

If you are going to use computer for a short time, and 2+2 option is cheaper, than you may want to consider it. For normal use you won't need more that 4 GiB anyway.

Of course, this all applies only if computer will actually work in such configuration. It may be smart to buy from some vendor which has good returns policy.

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    It's actually more complicated. It also depends on what memory combination the machine will support, and in this case it's a Mac, which has very strict memory requirements as far as the installation is concerned. – BinaryMisfit Sep 4 '10 at 17:55
  • @Diago♦ I know that they have temper, but this is a surprise. In the end, it's better to be safe than sorry, so you're right. – AndrejaKo Sep 4 '10 at 17:56
  • I have had the same issue with non Mac machines and especially notebooks. My Dell and the Acer I have has the same limitations. – BinaryMisfit Sep 4 '10 at 17:57
  • @Diago♦ If you're talking to me, than I'll have to do a lot more research in the future! I never had any problems with my Acer, but I do know that it doesn't support 4 GiB memory modules, so I didn't even try installing them. – AndrejaKo Sep 4 '10 at 18:04

Here is a long discussion on MacInTouch.com with a bunch of real user experiences (and opinions) about memory upgrades on a Macbook, and whether or not pairing RAM is good or bad.

Some useful info as well if you Google "pair memory macbook".

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