How much RAM can I install in my laptop?

There are six machines in the A1278 Model. Some will take a maximum of 6 GB of RAM and some will take 8. So Bac is the only one here that gave a correct answer. Machine identification is critical and answers given without that information are just guesses.

"according to various sources, including this one, and also Mactracker, you CAN install up to 6GB of RAM in the MacBook Unibody A1278 (aka MacBook Late 2008)

the same source mentioned above also mentions that real-world testing shows an almost negligible performance difference running match RAM modules vs running 2GB + 4GB"

"I installed 8GB in my late 2008 Unibody Macbook. Make sure you have the appropriate firmware upgrade:

http://blog.macsales.com/9102-secret-fir...

I first went from 2GB to 4GB....huge, night and day difference. Like a new machine.

Then I wanted more, and went from 4GB to 8GB...some difference. Not near as much noticability as 2 to 4. If I hadn't already paid for it, staying at 4 would have been fine.

But YES 8GB is fine. Few people, sellers, Apple....almost nobody will tell you this is okay. Oh yeah, and of course it voids the warranty in our 7 year old client ;)."

"Apple says 4 GB but some people have installed 6 GB. A 2GB and a 4GB.

Ralph"