OWC has found that there is a secret firmware update that allows MacBooks from 2008 (late 2008) to install 8GB of RAM.
At the end of 2009, an update appeared to solve excessive noise in the optical drive, but if you had your Mac updated to the previous version, the update did not appear. This update allowed to install 8GB of RAM in any MacBook, although it did not expressly put it.
It worked on the following models:
● MacBook 13.3 ″ 2.0GHz and 2.4GHz
● MacBook Pro 15 ″ 2.4GHz
● MacBook Pro 15 ″ 2.53GHz model with ExpressCard Slot (Late 2008)
● MacBook Pro 15 ″ 2.8GHz model with ExpressCard Slot (Late 2008)
Check your version of BootROM in System Profile and make sure it is MBP51.007E.B05 for MacBook Pros and MB51.007D.B03 for MacBooks.
If your version does not match the numbers above you have to download the following update:
● MacBook Pros (MacBook Pro5,1): MacBook Pro EFI Firmware Update 1.8
● MacBooks (MacBook5,1): MacBook EFI Firmware Update 1.4
Then make sure you have Snow Leopard 10.6.6 installed, which is where the tests have been done, and you can now install your 8GB of RAM.