Fun times: I'm getting 1400 kh/s on a Radeon 7970 with opensource Linux drivers. Default clocks of 950/1450 MHz and I estimate the power draw at 150 W max. (For comparison, my GTX 1070 does about 1600 kh/s at 100 W). I've seen my share of miners reporting wrong numbers, but this one is verified by a pool over a full day, so it's looking legit.

This is with Linux 4.15.12, mesa 18.0.0_rc5, llvm 6.0.0 and xf86-video-ati 18.0.1. It should be noted that the newer opensource AMDGPU driver isn't available for the 7970, but the real action for OpenGL/OpenCL is happening with Mesa and LLVM, and there have been some great developments.

I've been testing the opensource driver stack for a while, as I've sold most of my Radeons and I've stopped patching the old binary driver (fglrx) for newer kernels. So far, it's been slower, around 650 kh/s vs. 875 with fglrx. This incredible leap came after the latest Mesa and LLVM updates. It's been known for a while that the opensource stack outperforms the old binaries in many applications, but this is a first for me with miners.

While great for BBR, there aren't many other miners that work at all with the OS drivers. Newer miners use OpenCL 2.0 which isn't implemented yet, and there are other issues. So I guess I'll keep this machine for BBR only for now

Also noting this is a rather slow machine with 1x PCIe bus, but it's probably irrelevant for BBR mining.