Sometimes, Software Update is able to offer a "smaller-sized Delta" update than you might expect for Mac OS X v10.3.4 and later, or smaller than what you might see on other computers installing the same update. The "smaller Delta" updates are offered when some Mac OS X system files can be modified instead of replaced in their entirety. See "Why are some computers not offered a smaller update?" below for more information.
Smaller-sized Software Updates take less time to download and install than regular-sized Delta or Combo updates.
Tip: For updates that have different-sized versions, the "smaller-sized Delta" is the smallest. The regular-sized Delta version is the next smallest, and the Combo version is the largest (but most versatile).
How do I make sure I use the correct update?
From the Apple menu, choose Software Update. Then install the update(s) it offers. Software Update automatically finds the best update your computer can use. If you're updating more than one computer, it's possible that the size of the same-named update will vary from computer to computer. Just install whatever Software Update suggests.
Why are some computers not offered a smaller update?
Not every computer that has Mac OS X v10.3.4 or later can benefit from smaller Software Updates. Why? Sometimes, modifications made to Mac OS X system files, including ones made by third-party products, may require the installation of a full sized version of a Mac OS X software update. You don't have to worry about figuring out which kind of update is best for you, just let Software Update preferences do the work.
Advanced tip: Details about this process can be viewed in the /var/log/install.log file.
Can I install a smaller-sized Software Update on a computer that did not download it?
For best results, use Software Update preferences to update each computer individually, since not all computers may be able to use the smaller-sized update. If you just want to download an update once, you probably want to use a "Combo" update installer version, available from Apple Downloads.
Can I download the smallest-sized updates from Apple Downloads (standalone installer)?
No, the smallest-sized updates are only available from Software Update preferences built-in to Mac OS X, because Software Update needs to make sure your computer can use the smaller update before allowing you to install it. If it didn't do this check, you might end up with unusable system software files.
However, you can download installers from Apple Downloads (sometimes called "Web Updates"), even if they are not quite as small as installers that Software Update may offer.
How do I know if I installed the smallest-sized Software Update?
Look in your Receipts folder for updates that contain the word "patch". For example: MacOSXUpd10.4.6IntelPatch.pkg
Tip: Smaller-sized Delta Software Updates may not be not available for every Apple software product.