Graphics processors of the present design provide hierarchical open sectors and variable cache sizes for cache operations. In one embodiment, a graphics processor comprises a cache memory having a hierarchical open sector design including a first hierarchy of upper and lower regions with each region including a second hierarchy of sectors. A cache controller is configured to initially open a first sector of the lower region, to receive a memory request that does not match an address in the first sector, and to open a second sector of the lower region.