[markw10]

I purchased a C2D MBP last fall and because of the extra $500 or so for 3GB chose to go with 2GB. I'm sure memory has gone down in price some and most of all it's cheaper to buy elsewhere than Apple.
My questions:
Since I have 2GB of memory would each slot be filled up requiring me to purchase one 2GB stick to use with one of the 1GB sticks already installed or would it be just one 2GB stick allowing me to get a 1GB stick to add to it?
Is this something that is easily done by the user?
Most of all, what is the best memory out there? I want a reasonable price but don't want to buy anything that will cause stability issues.

[Simon]

Apple's 2 GB config on the C2D MBP comes with two 1 GB SO-DIMMs. So you will have to remove one 1 GB SO-DIMM and replace it with a new 2 GB SO-DIMM.

You can however use that 1 GB SO-DIMM in another MB(P), Intel iMac, or Intel Mm. You can also sell it to reduce the cost of the new DIMM. Just keep in mind that the original MBP warranty covers the two original DIMMs and not the new one (that one should come with its own warranty). Although I'm personally not worried about it, some people recommend keeping the old DIMM around in case you have to bring your MBP in for warranty repair. The idea is to prevent Apple from blaming some kind of LB problem on the user-installed third-party RAM.

The SO-DIMM swap is easily done by the user in two minutes. This Apple page shows you exactly how to do it. Good luck.

[fongyuen]

i'm looking to upgrade as well and i'm wondering why there's just a big price difference b/w crucial's 2 gb kit ($309) vs. owc's stick of 2gb ($146). also, anyone notice an appreciable loss in speed in using the diff. pairing of memory?

[Simon]

Originally Posted by fongyuen 

also, anyone notice an appreciable loss in speed in using the diff. pairing of memory?

You will not notice it.

Dual channel memory access (paired DIMMs) is most important when there is no dedicated VRAM and the GPU has to use the FSB to fetch from RAM what would otherwise be in dedicated VRAM. This is the case with the MB or Mm. On a MBP you have dedicated VRAM so this isn't an issue.

Other than in that case, there are very few benchmarks that are able to show a performance difference between paired and unpaired DIMMs. And in most cases the difference is within the reproducibility of the measurement. So it's certainly not something you notice in everyday work. Usually the advantage of having more available memory will by far outweigh any loss due to the unpaired DIMMs.

[markw10]

I'm thinking of getting the one in this link:
Newegg.com - CORSAIR ValueSelect 2GB 200-Pin DDR2 SO-DIMM DDR2 667 (PC2 5300) Notebook Memory - Retail
My question: Is it safe to pair that with one of the 1GB sticks in my machine or am I better off getting the matching version of a 1GB stick from Corsair?
As well, I know this will mean my memory is no longer dual channel but is it true that the extra 1GB far outweighs the loss of dual channel?

[Simon]

Originally Posted by markw10 

As well, I know this will mean my memory is no longer dual channel but is it true that the extra 1GB far outweighs the loss of dual channel?

Obviously if you never need more than 2 GB of RAM you have nothing to gain from 3 GB. But if you actually experience page-outs with 2 GB the loss of dual-channel memory access will be made up for by the reduced swapping. HDD access is by far slower than RAM access regardless if it dual or single channel. In that sense I think you can easily sum it up on a Mac with dedicated VRAM: I you don't need a lot of memory, make sure it's paired. If you need more memory, go for more even if it means giving up on dual-channel access.

Here's a quote I found on BareFeats:

DO MATCHING PAIRS OF MEMORY HELP?
Though we ran the tests above using matching 1GB SODIMMs in both MacBook Pros (for a total of 2GB), we also ran the same tests in the 15" MacBook Pro Core 2 Duo with one 1GB SODIMM and one 2GB SODIMM for a total of 3GB of memory. We wanted to see if non-matched modules would cause the MacBook to slow down due to the loss of interleaving.
The answer is "no, it didn't slow down." In some cases we saw a gain in speed. An example is Aperture where the "lift and stamp" ran 11% faster with 3GB of RAM. But that's probably due to the fact that Aperture + OS X = more than 2GB of total memory usage.

[chabig]

Here are some benchmark results for paired versus non-paired RAM in a MacBook.

[markw10]

I went into Activity Monitor to select pageouts. I don't use very powerful programs but do a lot of multitasking. Often I have Safari open with 4-5 tabs open within it and often both Word, Excel, and Entourage open. About 75% of the times iTunes is open in the background and around 50% of the time I have Parallels open with Windows XP running Quickbooks. I checked Pageouts with Activity Monitor running for just 5 minutes with the usual programs I have open and it was already over 40,000 so i think the 3 gigs definitely should help me.