6990 not working

[Jarvis2.4]

Hi miners,
I am making my 2nd Rig. The problem is I connected my 6850 on the 16X slot and I installed the latest catalyst. When I connect 5770 it detects it mines also. But when I connect my 6990 only Microsoft based driver activate in Device Manager. Sometimes the screen freezes during booting windows. I was using 1x to 16X powered riser for both 5770 and 6990. Do I need dummy plug?
The fan of 6990 Toggles and slows down and continue every 2 - 3 secs. Any Idea how to fix that. Need Help!

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[Equate]

Give some more details :-

Driver version ?
Mining software ?

6990 fans seem to be toggling due to over-use . You can oil the fans , it seems to help .

[Jarvis2.4]

Give some more details :-

Driver version ?
Mining software ?

6990 fans seem to be toggling due to over-use . You can oil the fans , it seems to help .

Win8 Amd 14.2 catalyst
The device is not detected properly in device manager. I am having TX 750 PSU. Fans are toggling to 100% then 10% for 5 seconds and this continue. CGMIner not detecting 6990 but 6850 only.
Thanks anyway

[Equate]

Can you try with old catalyst drivers , I have found 13.11 quite stable . If you have another rig , try to swap your cards and see if its gpu problem .