Apple has released the MacBook SMC Update 1.3 via its Software Update utility and on the Web. According to the company, polycarbonate MacBook computers released in early 2009 may display slower performance when started up using battery power only. You can resolve this issue by downloading and applying the update. The MacBook SMC Update 1.3 weighs in at 557KB and requires Mac OS X 10.5.6 or later.
Source : http://www.123macmini.com/