Latest FGLRX ADM X-window driver caused me problems
I just tried upgrading the AMD linux X-window driver 'fglrx64_xpic_SUSE122' from 8.982-1-x86_64 to 9.002-1-x86_64.

After installing, it appeared that my hashcat performance had dropped by 2x. Moreover, though I didn't copy down the exact kernel description in hashcat, it had changed from Tahiti_938.2_1.4.1741.kernel to something that included the string "VM".

I downgraded and performance returned.

Maybe something on my end, but I thought I would pass it on.
Yes, there is written on this forum on x places that you need to stick on 12.8 driver for a moment because with latest one multigpu will fail. Disable X and run hashcat-* as root and all performance will come back.