Just added my 9th card and have started having problems.  I'm using the 17.12.1 Adrenaline driver and can get all 9 cards recognised but 1 out of the 9 only runs at half hashrate.  Just working through the suggestions here to see if I can improve it.

One thing I'm finding is that when using the AMD settings app to switch the cards to compute, it runs really slow.  I saw a suggestion that a better CPU is needed - I currently have a G3900 - can anyone suggest the minimum I should be looking at?