The problem is that the 6990 contains of two 6970 chips which are Cayman XT and the 6950 contains of the Cayman Pro dispite the Shader unit amount difference their are other little problems indicated such as unequal RAM timings and other little unsimilarities which disturb the full synchronization of CF with the 6990 and the unlocked 6950 of yours.
In theory CF with any AMD model of card should be fine but the reality shows that it sometimes can cause some unstable operation of the gpu.
Consider that and make sure you have the latest drivers installed and CF fully enabled because even without 6950/6990 CF those scores seem pretty low.
got the above off another forum
im thinking of going trifire with this setup, i also have 2600k oc'd 4.4(for time being) 2 harddrives 7 120mm fans waterpump, will my nearly new corsair hx 850w handle it, i reckon it should but just wanted to make sure.
In theory CF with any AMD model of card should be fine but the reality shows that it sometimes can cause some unstable operation of the gpu.
Consider that and make sure you have the latest drivers installed and CF fully enabled because even without 6950/6990 CF those scores seem pretty low.
got the above off another forum
im thinking of going trifire with this setup, i also have 2600k oc'd 4.4(for time being) 2 harddrives 7 120mm fans waterpump, will my nearly new corsair hx 850w handle it, i reckon it should but just wanted to make sure.