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My MacBook is 6.1 2.26 Intel Core2 Duo, 1066 MHz FSB (MC207*/A). Corsair memory is Mac Memory 8 GB DDR3 SODIMM (CMSA8GX3M1A1333C9). It says "supports memory bus speeds of up to 1333 MHz". Is it safe to use on my 1066 MHz MacBook? Is it tested by Corsair? Couldn't find info on the Corsair memory finder or forums, but I found this link about problems of incompatibility by some incorrect memories con Mac computers that made me afraid of buying.

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store.apple.com/us/memorymodel/ME_13_2_26_MB_W_UNI is a link to what apple sells (PC3-8500) for what I believe is your laptop. I do not know if they require anything special from the mfg. however (some hardware (ati vidcards etc) requires special firmware version for apple; I doubt memory does, but you never know). Use the specs listed to match up corsair memory. –  horatio May 8 '12 at 18:17
    
Despite the fact that Corsair calls it a kit, the CMSA8GX3M1A1333C9 part number you reference in your question is a single 8 GB SO-DIMM. That means it will not work in your MacBook, which only supports up to two 4 GB SO-DIMMs (see my answer below for more info)--so in this case, the MHz rating is irrelevant. If you were talking about a 4 GB or smaller module, then the best advice would be to confirm that the memory is certified for your particular Mac, ask the manufacturer, confirm someone has used it without problems, or buy it from someplace with a generous return policy. –  rob May 10 '12 at 20:29
    
I ended up buying a 1066/1067 MHz 4GB "Apple" OEM (Micron chip) memory installed by a unofficial dealer of Apple products. Now I have 5GB and works like a charm. There are almost no more paging. Payed some more but it certainly works. –  Alejandro Iglesias May 10 '12 at 20:49
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I would personally only buy memory that has the same frequency that your computer is specifying… I once had such an experience and the computer didn't boot when I had the better RAM in… i just had to swap the old ones back in and it worked. I wouldn't know if they tested it in the fashion that you would like them to.

As a general rule… I keep to buying RAM that is clocked the same as the RAM that is known to work or RAM that is clocked the same as the RAM you currently have.

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All the RAM in the system will automatically be clocked down to the lesser of the slowest module's speed or the motherboard's highest supported speed. There was probably some other incompatibility issue in your case--for example, the density of the memory chips may have been too high, or the other timings may have been off. That said, your more general statement that you should only buy ram that is known to work in a given computer is good advice. –  rob May 8 '12 at 18:17
    
As has been stated... just because it's "clock" is the same is no guarantee that it will work. Also match voltage, CAS latency, etc... –  TheCompWiz May 9 '12 at 12:55
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According to Apple, your MacBook officially supports up to 4 GB (two 2 GB SO-DIMMs, one in each of two memory slots). According to Wikipedia, it looks like people have successfully upgraded to 8 GB, but they had to use two 4 GB SO-DIMMs.

So, to answer your specific question, no, the 8 GB Corsair memory module you mentioned will not work. You'll need to use 4 GB or smaller modules.

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I'm aware that there are tests that verified that my model supports 8GB and the Corsair model I cited is a blister with 2x4GB. –  Alejandro Iglesias May 8 '12 at 18:43
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According to Corsair's website, the CMSA8GX3M1A1333C9 part number that you referenced in your question is a single 8 GB SO-DIMM, not a 2x4GB kit. Several vendors also list it as a single 8 GB module. See corsair.com/… –  rob May 8 '12 at 19:12
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There's a lot more to RAM than its rated clock-speed. Just because one is faster than the other... does not mean it will work in that motherboard... and it's usually not because of the bus speed. Things like CAS latency matter. I would HIGHLY recommend you use a memory finder for your specific laptop... and go with what it recommends. Corsair has a very nice one that includes Apple Macbooks.

http://www.corsair.com/us/learn_n_explore/

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As I said in the question, I already looked in the Corsair memory finder, it doesn't have my MacBook model (6.1, model no. MC207*/A). –  Alejandro Iglesias May 8 '12 at 18:04
    
Crucial has a spiffy tool that can find compatible memory types for you. It appears that corsair doesn't have a guaranteed compatible module... but crucial does. crucial.com/upgrade/apple-memory/oem.html –  TheCompWiz May 8 '12 at 20:48
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As you've been told on another forum, in most cases if the motherboard or the CPU doesn't support 1333 MHz, it will automatically run at 1066 MHz. This is not guaranteed however!

The motherboard is built for a maximum of 1066 MHz, so you're better off with 1066 MHz RAM anyway. 1066 MHz RAM should be cheaper.

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