Abstract: A method, which may be embodied upon a computer readable medium and executed by a processor, for PCI IO using PCI device memory mapping in a logically partitioned system. The method may include the steps of detecting PCI devices in a bus walk initialization process, and associating a pseudonym address range with each PCI device detected in the bus walk initialization process. The method may further include updating PCI device IO resources for each PCI device detected with the associated pseudonym address range, and accessing the detected PCI devices with a device driver using the pseudonym address range stored in the PCI device IO resources.