Discovered this from OWC via iClarified, and thought it warranted further coverage.
OWC has discovered that a ‘secret’ firmware update has enabled access to 8GB of RAM on late ’08 MacBooks.
In late 2009, an EFI Firmware Update was released to address the buzzing noises coming from the optical drive. However, it seems that somewhere along the line, Apple changed this update without notating it anywhere.
Whether any other elements were affected by this change is undetermined, but it did change memory addressing; with the later version of the update installed, you could address a full 8GB in Snow Leopard. Unfortunately, Software Update doesn’t show this version as being different from the previous one, so users wouldn’t be notified if they had already updated their firmware to the older version.
This discovery applies to the following MacBook models:
● MacBook 13.3″ 2.0GHz and 2.4GHz
● MacBook Pro 15″ 2.4GHz (All)
● MacBook Pro 15″ 2.53GHz model w/ExpressCard Slot (Late 2008)
● MacBook Pro 15″ 2.8GHz model w/ExpressCard Slot (Late 2008)
Check your BootROM version in System Profiler and make sure its MBP51.007E.B05 for MacBook Pros and MB51.007D.B03 for MacBooks.
Then download and install the “secretly” updated firmware from here:
● MacBook Pros (MacBookPro5,1): MacBook Pro EFI Firmware Update 1.8
● MacBooks (MacBook5,1): MacBook EFI Firmware Update 1.4
Finally, make sure you are on Snow Leopard 10.6.6 then upgrade your RAM to 8GB.