Older Core 2 Duo MacBook and MacBook Pros from late 2008 may support 8 GB of RAM, according to hardware parts vendor Other World Computer. Other World Computer discovered that a newer version of the EFI, when combined with an updated Boot ROM, would let the computer use the full 8 GB of RAM without slowdowns or crashes. EFI is the Mac equivalent of the BIOS firmware on IBM PCs.
Previous tests by Other World Computer revealed that these older Macs could accept 8 GB of RAM, but would come to screeching halt when an application tried to use the full 8 GB. The optimal RAM was assumed to be 6 GB according to tests by OWC. Despite this presumed limitation, reports circulating on the internet continued to suggest the older MacBook models could effectively use 8 GB of RAM with Snow Leopard.
OWC discovered that Apple released a new version of the EFI for these older MacBooks in 2009. This update was designed to reduce the noise from optical drives. OWC noticed that Apple modified the memory addressing in the update and did not notify anyone of these changes. OWC claims the Mac OS X software update does not recognize this latest version as new and does not prompt people to upgrade. Unbeknownst to them, most MacBook users continue to have the old code, which supports 6 GB.
After upgrading the EFI manually and installing the updated Boot ROM, OWC was able to efficiently access the full 8 GB of memory. This is good news for folks with an older MacBook as the 2 GB addition may give older models enough of a boost to stay in service for a little longer.