The updates were released to improve FireWire disk operation, networking and system stability, and are designed for machines running Mac OS 9.1, which is also Mac OS X's Classic environment for un-Carbonized applications.
These are designed to support US English Macs, but International English versions are likely to be released soon, say industry pundits.
Weekend reports claim that Apple's firmware updates host an unexpected bug, in which some Macs using third-party RAM upgrades can't recognise installed memory after the updates are installed.
In these cases, the Mac only recognises Apple-installed and AppleStore-provided RAM. A number of third-party memory products are recognised, however.