MacSales may have uncovered a secret firmware update that will allow older MacBooks and MBPros to use 8GB of RAM.

The information originated in Mac Forums.

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.

That means if you want to add 8GB of RAM, and you have one of the affected models, you can upgrade your computer to 8GB of RAM.

  • 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)

Here’s how: check the Boot ROM Version in your System Profiler.

  • MacBook Pros with a Model ID of MacBookPro5,1 should have a Boot ROM Version of MBP51.007E.B05.
  • MacBooks with a Model ID of MacBook5,1 should have  a Boot ROM version of MB51.007D.B03
  • Machines with other Model IDs are not affected and don’t need an update.

If your Boot ROM version does not match the numbers above, download the appropriate firmware updater for your model machine and install according to the instructions:

  • For MacBook Pros (MacBookPro5,1)
  • MacBook Pro EFI Firmware Update 1.8
  • For MacBooks (MacBook5,1)
  • MacBook EFI Firmware Update 1.4

This is a pretty incredible find, we’re not so sure why it wasn’t made public earlier.  Oh and here’s 8GB of RAM for $90 which may help out a few of you this morning.