Storage and upgrade vendor Other World Computing took another look at the memory limits in some of Apple's late 2008 Core 2 Duo MacBook and MacBook Pros. Its testing found that a specific blend of updated firmware, Boot ROM and OS versions will let the notebooks handle a 8GB RAM upgrade.
Posted recently in the company blog, the tip says that machines running the latest update to Snow Leopard can address 8GB rather than the previous 6GB limit. It all depends on which version of the EFI Firmware Update and Boot ROM is installed.
The practical upshot of all this is that if you installed the EFI Update when it first came out, like we did, you would have gotten the old code, which meant your computer would only address 6GB properly. Those who didn’t upgrade until after Apple changed the updater got the newer firmware, which allowed proper addressing of 8GB.
Once we manually installed the “updated” version of the EFI Firmware in our test machines, they were able to address 8GB normally, without any crashing or slowdowns.
Users may have to download updated Boot ROMs, make sure they are running OS X Snow Leopard v10.6.6. According to the blog post, the machine must run the 10.6.6 software.