A new GPU ISA manual is available for AMD GCN 3rd generation GPUs. This is probably regarding the Tonga GPU and Carrizo APU as it mentions that context switching is an additional capability to the architecture.
You may download it here:
http://amd-dev.wpengine.netdna-cdn.com/wordpress/media/2013/07/AMD_GCN3_Instruction_Set_Architecture.pdf
