I have an old R295X2 card which I have tried to install it on linux for ages.
Due to the problem with Xorg which you might have read from other sources, AMD stops develop the driver for old cards and we have stuck with a choice to either use very old linux system in order to use AMD old driver or use opensource driver.
Mesa OpenCL now works very well with my card, I can see 2 GPU and mixbench yields almost theoretical FLOPS.
So if anyone out there looking for a way to use old Radeon GPU, just go with Mesa/open-source driver.
