MP-capable operating systems will be able to run without special customization on multiprocessor systems that comply with this specification. End users who purchase a compliant multiprocessor (MP) system will be able to run their choice of operating systems. The MP specification covers PC/AT-compatible MP platform designs based on Intel processor architectures and Advanced Programmable Interrupt Controller (APIC) architectures. The term PC/AT-compatible here refers to the software-visible components of the PC/AT, not to hardware features, such as the bus implementation, that are not visible to software. An implementation of this specification may incorporate one or more industry standard buses, such as ISA, EISA, MCA, PCI, or other OEM-specific buses. To encourage vendors to deliver solutions based on the MP Spec, Intel is making the copyrighted specification itself freely available to the industry.