BeOS was an OS developed to run on the BeBox hardware, a custom PowerPC based platform optimized for multimedia I/O. Early prototype hardware was based on the AT&T "Hobbit" microprocessor. The OS was first released in October 1995 for the BeBox, followed by a port to the Apple PowerPC platform the next year. An Intel x86 port of the OS began in March 1998 with version R3. The last version released was R5.1 in November 2001 for x86 only. BeOS is POSIX compatible but is not a UNIX derived operating system