Abstract: A method and apparatus is disclosed for initiating execution of selected application processors in a clustered multiprocessor system without disrupting the addressing mode of the processors. In one embodiment, this is accomplished by initializing the processors in a conventional way, setting the addressing mode, and then leaving each of the processors in an active mode spinning on a designated Startup Address Location. To start an application processor, the OS simply write a target processor ID and a desired start-up address into the Startup Address Location. The application processor with the matching processor ID reads the Startup Address Location, jumps to the address specified in the Start-Up Address code section, and begins execution at that location. In another embodiment, a processor is provided that does not switch addressing modes when switched from a halt state.

Abstract: A method and apparatus for increasing the routing bandwidth of interrupts between cluster manager devices in a clustered multiprocessor system is disclosed. This is accomplished by providing special cluster manager devices that can convert “N” serial messages received from a local APIC to “M” parallel messages, wherein M is less than N. The special cluster manager device then transfers the “M” parallel messages to a receiving cluster manager device. The receiving cluster manager device converts the “M” parallel messages into the original “N” serial messages, and sends the “N” serial messages to the appropriate local APIC within the receiving cluster.