According to the manual for my macbook pro, I can install a maximum of 4GB of RAM via 2 x 2GB modules. However, when I go to the apple online store to purchase the memory modules, there is an option for a 4GB module. So, am I choosing between 2 x 2GB modules and 1 x 4GB module? Are there any performance implications of having one module versus two? Can the machine actually handle more than the stated 4GB?
MacBook Pro, Mac OS X (10.5.8)
How much RAM your machine can really use depends on its Model Identifier, which is shown in System Profiler > Hardware Overview. If you have a MBP 3,1 it can use 6GB (one 4GB and one 2GB module) even though Apple only supports 4GB. If you have a MBP 2,1 or 2,2, it can only use 3GB, even if 4GB is installed.
Apple's maximum-RAM specs tell what amount of RAM Apple has tested the machine with prior to its release, which of course is dependent upon the availability of RAM modules to test with. No 4GB modules of the right type were available when your machine model was in pre-release testing, so Apple only tested it using two 2GB modules. Apple doesn't go back and retest older models with larger RAM modules as they become available, so the original RAM specs are never updated. Third parties often do follow up by testing with newer, larger RAM modules, and their findings sometimes show that larger amounts of RAM will work. In the case of your model, 6GB works fine, but 8GB has been found to make the machine unstable.
Using matched pairs of modules provides a small performance benefit that unmatched modules can't deliver, but the loss of that benefit with unmatched modules is greatly outweighed by the benefits of having more RAM if you actually need more. If you don't need more RAM than you have now, installing more won't improve anything, and installing two modules that don't match will actually slow things down a little (very little).
The Mid/Late 2007 15" 2.2/2.4 GHz and the Mid/Late 17" 2007 2.4 GHz can handle up to 6gb ram. You would put a 4gb module in one slot and a 2 gb module in the other. Do not leave one empty. Also, never purchase ram from Apple, they overcharge for it like no ones business. You can find it elsewhere online extraordinarily cheaper, like here for example: http://eshop.macsales.com/shop/memory/Apple_MacBook_MacBook_Pro/Upgrade
My machine is a "3,1" model. So, now I'm wondering why Apple supports only up to 4GB if one can use up to 6GB. There must be a reason, right? Am I going to lose anything by installing 6GB? I wonder if they do something special when there are two same-size modules, which they won't do if the modules differ in size. And if so, is the benefit of the extra 2GB canceled by the elimination of this special caching (speculation, of course) or whatever?
I'm running Lion v10.7.5, with all of the latest updates, and I put a "matched" 4GB & 2GB module in, from Other World Computing (OWC), which due to the mis-match in size, would slow-down the machine from 5%-10%.
I just have one issue -- due to "memory leaks" in the processes, the Activity Monitor shows that, over 2-weeks-of-uptime, I eventually run-out of the 6GB, and have to resort, possibly, to swapping.
That is when everything goes-to-perdition !
The swapping just doesn't seem to work, and everything stalls (won't respond).
I'm wondering if this is a result of the fact that some memory-addressing-chip inside of the machine, is not built for over 4GB of RAM.
My Mac, delivered Nov. 1, 2007, was on the "cusp" of mid/late-2007, so I have a 7,200RPM 200GB hard-drive in it, which you would think would be ideal for Virtual Memory.
Yet, I cannot get a definitive answer from Apple on this.
Why would you need over 2 weeks of uptime?
Ideally, you should never want your HD to use up memory. It just slows your mac down.
Your mac can handle 6gb of ram with minimal performance hit. And nothing can replace more RAM.
How much memory can my 2007 macbook pro use?
