1. A computer system, comprising: a cache memory having a plurality of data sets with each data set having at least one data entry, each data set having an index value for accessing the data set and each data entry having a tag value for determining a hit; and at least two domains sharing the cache memory, each domain having an address space including a plurality of memory addresses with each memory address having a tag field with tag bits and an index field with index bits; each of the domains configured to request data from the cache memory by extending the memory address of the domain from which the request originates with an address space identifier having at least one bit unique to the address space.