Method of mapping multiple address spaces into single pci bus

Abstract

A method and apparatus are provided for mapping multiple address spaces into a single bus, such as a single peripheral component interconnect (PCI) bus. The single bus is coupled to a first processor complex and a second processor complex. An original address of a memory access is shifted to a unique address space for each originator/target of an operation. The shifted address is used on the single bus. Then the shifted address is shifted back to the original address for completing the operation on a destination bus. The original address of a memory access is shifted to a unique address space for each originator/target of an operation using a respective predefined value (+X1, +X2, or +X3) for shifting the original address above a predefined boundary for each originator/target of the operation. Shifting back the shifted address to the original address for completing the operation on the destination bus uses a respective predefined value (−X1, −X2, or −X3) for the shifted back address to the original address for completing the operation on the destination bus. Using the shifted address on the single bus utilizes a dual address cycle (DAC) of the single bus for the shifted address. Completing the operation on a destination bus utilizes a single address cycle (SAC) of the destination bus for the shifted back address to the original address.