I have noticed several threads online, specifically this forum, where Linux users are misleadingly talking about how well their Radeon HD 5770 is working in their linux systems, failing to mention that they're talking about dual boot setups and also failing to mention that the performance they're talking about is on a Microsoft system.
The ATI Radeon HD 5770 Card is not supported by any linux version of catalyst, despite the Catalyst documentation claiming that support for this card was introduced in Catalyst 9.11, and despite it being listed as a supported card in 9.12.
I've been in touch with several reps at ATI/AMD and the response I got was that the linux driver was offered 'as is' and that their support wasn't official. That's actually the only support that was given. Period. "A deal is a deal, sucker!".
By 'not officially supported', I think the rep meant "we are not going to support it at all"-- as indicated by ATI/AMDs true failure to get a working driver for this card going.
I've tested this card's compatibility with almost all mainstream linux distros to find that the catalyst driver versions 9.11 and 9.12 (and the hotfix as well), while claiming to support this card, actually do not support the Radeon HD 5770. If someone is telling you otherwise, they are either lying or poorly communicating that they are using the driver on a Microsoft Operating system.
What I have not tested, is support in the Red Hat Enterprise, OpenSUSE, or Ubuntu distros as the version of catalyst for these distros is a special build tailored to those specific distros (and is designed not to work with other distros). Why, oh why, would AMD promise to fix the proprietary attitude that almost wiped ATI out of the industry (which necessitated their buyout) only to follow up with the exact same kind of customer-alienating behaviour?
So, if you need to use a linux system, and some people do, have a backup card-- this thing is a paperweight until someone at AMD reads this and realizes that people are going to eventually associate their brand name with these kinds of problems if they don't start tailoring to the compatibility needs of their customers.