Early eMac models natively boot Mac OS 9.2.2 and Mac OS X beginning with OS X 10.1.4, while later models only boot Mac OS X, also requiring a minimum of version 10.3. With the exception of some non SuperDrive equipped 1 GHz units, models 1 GHz and faster cannot boot OS 9, while eMacs slower than 1.0 GHz do not officially support 10.5 (requirements are an 867 MHz G4 with 512 MB RAM). No model of eMac can run the retail release of OS X 10.6 ("Snow Leopard") or higher, because Snow Leopard requires an Intel-based processor. However, there is a beta build that can run on PowerPC systems.