In 1991, Apple partnered with long-time competitor IBM and Motorola to form the AIM alliance. The ultimate goal was to create a revolutionary new computing platform, known as PReP, which would use IBM and Motorola hardware and Apple software. As the first step toward the PReP platform, Apple started the Power Macintosh line in 1994, using PowerPC processors from Motorola and IBM. These processors used a RISC architecture, which differed substantially from the Motorola 680X0 series that were used by all previous Macs. Parts of Apple's operating system software were rewritten so that most software written for older Macs could run in emulation on the PowerPC series. Apple also refused IBM's offer to purchase the company, but later unsuccessfully sought another offer from IBM, and at one point was "hours away" from an acquisition by Sun Microsystems.