I have a AMD Firepro v7900 what drivers should I use?

Currently not working and it should have 2gbs. any ideas?
ethminer --list-devices
CL_DEVICE_GLOBAL_MEM_SIZE: 2 147 483 648
CL_DEVICE_MAX_MEM_ALLOC_SIZE: 536 870 912 -->500MB (DAG FAILS)