Sad AMD can't fix their problems.

The multi-GPU 100% CPU bug has been around since dawn of mankind (actually I think it is v11.5?).

Then rather than fix it AMD ignores it for a half dozen versions and then somehow caused single GPU to ALSO get the 100% bug in Catalyst 11.7. 
It takes then 2 version (6 months) and they fix it for single GPU and keep the bug for multi-GPUs.  This despite their being an open bug report in AMD forums for over a year.   

Not only that people researched the pre-release version of 11.9 driver and CONFIRMED it fixed the 100% bug on single GPU but the bug remained on multiple GPU.  AMD answer is they don't do hotfixes and it may be included in the next driver version. 

If Nvidia didn't suck at hashing I would drop AMD forever and never look back (and this is coming from a long time "AMD fanboy" in my younger years).