set enviroment var GPU_FORCE_64BIT_PTR=1 end run again.
nou beat me to it
AMD should make this the default (and fully support it), at least for card with 4Gb+
For the Kaveri APU it should be the default. Especially under 64 bit OS's
(or is Kaveri limited to 2GB below 4GB because of lack of vision by BIOS developers)
This configuration solved my problem:
It reports coherent data, and 3768MB global memory.