I just learned that some folks are using 6 GB of RAM in MBPs that are supposed to only work with 4 GB. In my MBP (early 2008), I am running 2 2 GB chips. I am considering replacing one chip with a 4 GB chip. 8 GB does not work so well, apparently.

Here is the discussion link where I learned of it:
6GB in MacBook Pros; Yes it works. - 8GB... well... - Mac Forums (http://forums.macrumors.com/showthread.php?t=573906)

I'm interested in having 2 more GB of RAM since I often use VMware Fusion to run XP, and I commonly have FCP, Compressor, and Photoshop open at once (OK, Firefox, too).

There is disagreement as to whether the extra 2 GB of RAM is worth the hit you take not running in dual channel mode (two matched pairs are needed for dual channel). Assuming that the extra 2 GBs keep you from accessing your hard drive, I THINK there would be speed gains with the extra RAM.

Any experiences out there?

If you are looking for improvements in Final Cut you will see none. If I am not mistaken Final Cut only can use 4 gigs.

If you are looking for improvements in Final Cut you will see none. If I am not mistaken Final Cut only can use 4 gigs.
what he said

Guys, David could not have made it any clearer that his interest was in the extra RAM for running multiple apps simultaneously + a Windows XP virtual machine

I'm interested in having 2 more GB of RAM since I often use VMware Fusion to run XP, and I commonly have FCP, Compressor, and Photoshop open at once (OK, Firefox, too).

So, if Chris and Pete are right and FCP can use up to 4 GB of RAM, then a MBP with 6 GB is going to run better. The OS has to use RAM, too. I'm not sure how much the OS needs, but I'm guessing the 2 extra GBs will help.

If I decide to go from 4 to 6, I will do some tests with 4 and then repeat them with 6. The rendering speed without the dual channel benefit of matching pairs is my main concern.

Thanks again,

DB

There is disagreement as to whether the extra 2 GB of RAM is worth the hit you take not running in dual channel mode (two matched pairs are needed for dual channel). Assuming that the extra 2 GBs keep you from accessing your hard drive, I THINK there would be speed gains with the extra RAM.

Any experiences out there?

"late 2008" MacBook Pro - 4GB vs 6GB RAM config (http://www.barefeats.com/mbpp11.html)

has some tests on this. Bottom line is that not using two matched pairs is at most a very minor hit.

So, if Chris and Pete are right and FCP can use up to 4 GB of RAM, then a MBP with 6 GB is going to run better. The OS has to use RAM, too. I'm not sure how much the OS needs, but I'm guessing the 2 extra GBs will help.

If I decide to go from 4 to 6, I will do some tests with 4 and then repeat them with 6. The rendering speed without the dual channel benefit of matching pairs is my main concern.

Thanks again,

DB

The question is whether the programs you want to run can "see" the extra 2 GB and whether the OS can properly distribute the tasks to the RAM. Photoshop might be a problem. Right now Apple doesn't support over 4 GB in the laptop line and there might be a reason in Leopard's programming.