Will OS X El Capitan slow down my Mac?

Episode 1254 (59:30)

John from Los Angeles, CA
Mac OS X El Capitan

John installed the latest version of iOS on his iPhone and it runs slower. Will that happen if he updates to OS X El Capitan on his Mac? Leo says no. It's a different animal. iOS 9 probably slowed down his iPhone 4S because it's old for a mobile device. But with a desktop operating system like OS X, it should do better on older hardware. Leo also thinks that Apple isn't sure why iOS slows down the 4S. Leo also says that putting a new hard drive in his Mac may be a good idea. An SSD is even better. It'll really speed up that laptop.