I was thinking of replacing the current 1 gb setup and going to 4gb,although I heard it only will use 3gb max. I have 2.16 core 2 duo macbook pro and have heard even the new 2.2-2.4 setups have the same issue.

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I have the same model 15" MBP. Without getting into the long technical discussion about matched vs. unmatched pairs, my advice is that if you can get two matching 2gb memory sticks at a competitive price over buying one 2gb stick, go that route. Otherwise, just grab a 2gb stick and carry-on.

See here for a little more info.. http://www.macworld.com/weblogs/edit...kram/index.php

-Aloha

Newegg.com. It's so cheap and easy to buy memory now that there's no reason not to max it out. 3GB does provide a small yet palpable increase over 2GB. Just stick the 4GB in and go. The extra gig won't be used but it doesn't cause any problems in the MBP at least (or hasn't for me, anyway).

Does the 2.2 model use all 4gb unlike the 2.16?

The newest ones use all 4GB, as in the ones they've been selling for the last few months at least. That would be the current 2.2 and 2.4GHz models (and the new 2.6GHz option). That may have been the first revision that was able to use all 4GB, but I'm not 100% sure about that part. I just know that the current ones can address all 4GB.

It's possible there is a previous 2.2GHz model that can't do it. I didn't look up all the previous speeds and stuff. It's a revision of the Intel chipset used that is responsible for the change.

The first question you need to ask before upgrading your RAM is: are you currently running out of RAM? Do you truly need more? Honestly, the average person doesn't need more than 2GB of RAM (maybe even 1GB of RAM) unless you are using memory-hog MS Vista. OS X and Windows XP need less RAM in general...UNLESS you are running memory-intensive apps like Photoshop or opening two dozen windows at once. Whenever you edit an image in Photoshop, it eats RAM (the larger the image, the more RAM). If you are merely surfing the web, watching videos, and editing Office documents, you're surely not going to need more than 2GB.

If you aren't already running out of RAM, you won't notice the slightest difference in performance by adding more RAM. It's like increasing the size of your car's gas tank to try to increase the range of your car, when the longest trip you make is to the grocery store. Having a larger gas tank won't make any difference for that sort of trip.

While RAM may be cheap now (really cheap), it's also a waste of money if you don't need it. I'd stop at 2GB unless you really do need more.

Another RAM hog is running a Windows environment under something like Parallels. Ideally you want enough RAM for the entire emulated RAM of the Windows system on top of the emulation software itself. That's probably over a gig total.

Wasn't it the Duchess of Windsor who said "You can't be too rich, or too thin, or have too much RAM?"

I'm pretty sure it was Bill Gates who said "Why on earth would anyone want more than 256KB?