The present invention provides a shared instruction cache for multiple processors. In one embodiment, an apparatus for a microprocessor includes a shared instruction cache for a first processor and a second processor, and a first register index base for the first processor and a second register index base for the second processor. The apparatus also includes a first memory address base for the first processor and a second memory address base for the second processor. This embodiment allows for segmentation of register files and main memory based on which processor is executing a particular instruction (e.g., an instruction that involves a register access and a memory access).