This firmware is designed for Mac OS X versions prior to 10.2 and is unnecessary for users of 10.2 or later.
However, the good news for those already operating on OS X 10.2 is that an update will be unnecessary. You can rest easy knowing that your system is already optimized to get the best performance out of the software.
In summary, if you're running an earlier version of Mac OS X, this firmware update is definitely worth considering. It will undoubtedly boost your experience and elevate your productivity to the next level.
Version 1.5.6: N/A