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I'm considering upgrading my end of 2006 MacBook Pro RAM. Yet I'm hesitating: it will not support 4GB of RAM, but only 3GB (I have 2x 1GB at the moment).

This means that each slot will have a different amount of memory, and I read somewhere that would prevent it from using double data rate or something like this.

Do you know if this decrease of performance is noticeable? Is it worth the extra 1GB of RAM? I'd welcome advice; especially if you have done so yourself. Thanks!

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You might know already the discussion here:

If you are actually limited by RAM, then I would not assume that the performance impact of a mixed 1GB/2GB setup would change much. Swapping to disk is so slow, it's hardly compensated by RAM timing issues.

However, first make sure that RAM is actually your issue.

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Thanks for your link, I had seen it. Basically it says that I can install 2x2GB, and get a increase in RAm (up to 3,2GB) without any performance hit, which is what I'v' just ordered. Thanks! :-) – Fabien Aug 8 '11 at 22:38

Realistically, a nearly five year old Mac is nearing its end of life, and I would ask if it makes sense to spend any money upgrading it. Sure, Macs can last forever (I used a 1989 SE/30 for 14 years as a mailing list server), but I don't think there's a good cost-benefit ratio for things like RAM upgrades with your Mac. The money would be better spent saving for a new Mac notebook.

To the exact point you raise, the unmatched RAM may slow things down a bit, but the slowdown is a "lower benchmark number" type, not a "noticeable in the real world" type.

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well if a $20 RAM stick can extend its life a little bit more, he could have save up until next year when a cooler laptop is out :) – Enrico Susatyo Aug 7 '11 at 23:59
Exactly! I just ordered 2x 2GB or ram for £35. A new MBP is £1550. Not really the same ballpark! – Fabien Aug 8 '11 at 22:39

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