Mar 8, 2011 13:27 GMT  ·  By

It has been revealed that a 2009 EFI firmware update from Apple contains code that allows certain MacBook computers to address a total of 8GB of RAM without hiccups, whereas tests carried out on the respective machines showed a cap of 6GB before the system started to shake.

The explanation comes from Other World Computing (OWC), a seller of computer hardware, accessories, and repair kits.

In a blog post, OWC notes that memory vendors, as well as some Late 2008 MacBook/MacBook Pro users, “have laid claim to these machines working with 8GB of RAM.”

“This was contradictory to our testing in December 2009 which quite clearly showed that while these models recognized a full 8GB, if an application addressed more than 6GB, the system would slow down significantly,” OWC writes.

So they had another run of tests, this time with MAc OS X 10.6.6 versus 8GB, and got pretty much the same results.

Then, they remembered about a late 2009 firmware update from Apple, tasked with addressing some problems with the optical drive in some MacBooks.

After looking at its underlying code, OWC claims to have found 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,” the computer experts reveal.

Since Software Update doesn’t show this EFI firmware update as being any different from the previous one, users are not notified of its existence.

However, the update can be manually installed. Those who own one of the systems listed below are eligible for the 8GB memory upgrade, OWC says.

- 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)

Coincidentally (of course not), OWC has some of the most nifty deals on MacBook memory kits. So you can upgrade today.