Usually with a new operating system version, some Macs are left behind as their hardware simply can't keep up with the advancing software requirements. For example, all Macs powered by at least Intel Core 2 Duo processors were able to run OS X 10.7 Lion, but when Apple launched OS X 10.8 Mountain Lion, some iMac, MacBook, MacBook Pro and Mac Pro configurations with Core 2 Duo CPUs were no longer supported. It seems that with OS X 10.9 Mavericks, however, all Mountain Lion-capable computers will be able to take advantage of the upgrade cycle.