I ran aticonfig --odgc --adapter=all for the rig that drops after a min. 

On boot, it's still running at 2.5-2.6 Mh, all 4 GPU's data are the same.  eg. core, mem are 1025,1400, bus speed is 5000:

http://i.imgur.com/WBSL7Gr.png

After a few mins it started dropping down to 2.3 Mh.   ALL GPU's data remained the same.  eg. core, mem are 1025,1400, bus speed is 5000:

http://i.imgur.com/7N8EPpu.png

So, nothing really changed at all from the GPU's setting perspective....


On my other rig that held steady at 2.77 Mh/s now over 15 hours at this speed, core, mem is the same as my other rig, BUT bus speed is only 2500

http://i.imgur.com/ypvTYVh.png

Any one know how to set bus speed independently so I can test further to see if that has anything to do with it??