Please use the 12.1a preview release driver as it should work fine with both cards.
But with 12.1a preview the 100% CPU bug is back!
Seriously, AMD, get your s**t sorted!
[Edit]: And the webpage says:
Applicable Products:This article applies to the following configuration(s):
AMD Radeon HD 6000 Series
AMD Radeon HD 5000 Series
... no word about 7000 Series.
Those are the devices that have 'official' support, but since it is a preview driver, it does not have 'official' support anyways. The preview drivers often have experimental features enabled which can cause unintended side effects which might not show up in the official release.