Communication among partitioned devices

Information objects and system firmware for a processor in a partitionable computing system are disclosed. One object comprises information corresponding to components of the computer system. The information comprises entries defining an address and a size for registers normally accessible to other partitions. The registers are capable of defining an address area such that in use the processor is arranged to permit other partitions to access at least one address area defined by the at least one register and to deny other partitions access to address areas other than the at least one accessible address area.