Here is an excerpt from the news of 06.03.2008:
Quietly, Apple has changed apparently one of his published in 2009 firmware updates. It is an EFI update that time should reduce the drive noise. Apple has so far this changed later according to the findings of MacSales that in the older models now up to 8GB memory can be used.
The devices affected is the white MacBooks (2 or 2.4 GHz) and the 15-Zoll.Modelle of MacBook Pros (2.4GHz / 2.53GHz / 2.8GHz) that from the end of 2008 were sold. Who installed the original update, you must install the now modified firmware later manually in order to extend the work to. Check allows the firmware version with a look in System Profiler and a comparison of model identification with the boot ROM version. For the most recent version MacBookPro5,1ist MBP51.007E.B05, for MacBook5,1 version MB51.007D.B03.
If the versions do not match, the MacBook EFI Firmware Update 1.4 or downloaded the MacBook Pro EFI Firmware Update 1.8 and newly installed.