New features included Time Machine automated backup, Stacks, and Cover Flow.īut with every big step forward in features and performance, the Mac OS leaves some older Macs behind. Where Mac OS X 10.4 Tiger had come in separate versions for PowerPC and Intel Macs, the Leopard installer could run on both platforms, and the version of Mac OS X installed could boot either type of hardware. Leopard itself was also a unified operating system. For the first time, a version of OS X was certified as Unix, and the new unified appearance makes Leopard friendlier and less confusing for users. Mac OS X 10.5 Leopard, released on October 26, 2007, was the biggest change to Mac OS X since Apple first released OS X 10.0 in March 2001.