Blender will drop support for GCN 1.0 cards starting from version 2.79 due to unsolvable issues.
Please AMD, update the drivers for GCN 1.0 cards so that Blender developers could integrate it in post 2.7x and 2.8 version.
Did you contact the Blender Stack Exchange to ask for more information regarding why GCN 1.0 Cards are no longer supported?See: Blender Stack Exchange Is this an issue in the AMD Drivers or because of a fundamental difference between GCN 1.0 and GCN 2.0 architecture?
Information non the current OpenCL Status for Blender is here: Dev:Source/Render/Cycles/OpenCL - BlenderWiki
Assuming you are on Windows:
I just checked for the latest HD7900 series Drivers Download (I am attempting to repair my card) to check if Driver support has been dropped. The Latest WHQL Driver for Windows 8.1 64bit, is 17.4.4 and there is an optional 17.7.1 Driver. So I would say driver support is dropped on Windows 8.1 64bit. However there are still Windows 10 and Windows 7 Drivers available for HD7900 series as recent as 17.8.2 Driver.
I am pretty sure there are lots of people still running HD7970/R9280x series cards for OpenCl and Rendering. If Blender Report back and say it is because they are using some GCN2.0 features specifically, and they are not prepared to put in the effort to write code for GCN1.0 cards then I cannot see there is Much AMD could do. I would guess you will have to stay on earlier versions of Blender in that case.
If Blender report back and say that there is some specific bugs in the AMD Drivers then ... I guess you can submit an AMD Reporting Form? AMD Issue Reporting Form
I have the same issue as you. I have an HD7970 and an R9 280x.
Please let me know if you wiill chase your own question up. I am pretty busy and I have a pair of GCN 3.0 (R9 Nano) cards so I can still use the latest versions of Blender.
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