Apple today began large-scale testing of its planned maintenance and security update for the Snow Leopard operating system, the Mac OS X 10.6.3. The new version originally entered the beta stage in early December of 2009, and will be the third instalment in AppleĆs line of Snow Leopard performance enhancement updates. In total, the upgrade is expected to deliver 221 code corrections and up-to 92 system components, dealing with a wide range of apps including MobileMe, iCal, and QuickTime Player 10.