PowerPC Reference Platform.
It was supposed to be IBM's challenge to the Intel hegemory. A standard PC design with a PowerPC processor (co-developed with Motorola and Apple).
Predecessor to the Common Hardware Reference Platform. Apparently, the proprietary box makers didn't like the legacy ports, and the PC makers didn't like the lack of compatible software.
Especially the BIOS. A notable deficiency is the lack of OpenFirmware, so though they had expansion slots, the only cards that would work for booting were cards made available for the device back when it was new. IBM and Motorola PReP machines weren't exactly compatible with the same cards, and Apple stuck with NuBus and highly specific processor bus slots until CHRP came out. | 
