No, Hawaii doesn't have DCC.

The issue can indeed be that there is not enough address space. Mesa doesn't
unmap most buffers, because mmap is a very costly operation. Such buffers are
only unmapped when destroyed. This is obviously a problem on 32-bit. Possible
solutions:

1) Always unmap buffers at appropriate places. This can have a significant
performance cost in CPU-bound apps.

2) Clear pb_cache on mmap failure and try mmap again.

(pb_cache typically contains staging buffers, which are always mapped.
Therefore, pb_cache completely hides allocation, GPU mmap, and CPU mmap
overhead, but it also contributes to address space usage.)