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Title: XFX Radeon 6950 ZNFC v 3 oddities Post by: resultsmayvary on June 28, 2011, 07:41:50 PM OK...so I just purchased 2 of the aforementioned cards from NewEgg at the same time. After they arrived I installed them and started guiminer. Both were running around 317mhps at 800mhz clock speed.
Here's where it gets interesting. In CCC, one of the cards allows memory clock settings from 625mhz - 1325mhz. The other card only allows 1100-1325. So I loaded up MSI afterburner and attempted to further tweak the cards. I was able to get them both functioning properly at 1.2v and 900mhz which produced 352mhps...on ONE of the cards. The other card immediately dropped to 250mhps. I dialed the second card back to 1.1v and 800mhz and it jumped back to 317mhps. In addition to this, the card that performed worse (card A) when overclocked runs a lot hotter than the other one (Card B). When they are both at 800mhz, card A is around 83c while Card B is at 72C. Any thoughts, suggestions, input, etc would be greatly appreciated. I wonder if Card A is defective... Thanks! Title: Re: XFX Radeon 6950 ZNFC v 3 oddities Post by: Draradech on June 29, 2011, 07:45:20 AM I also have 2 XFX 6950s which are showing weird behavior, although it is consistent between the two cards. Ram speed is also key to speed on these cards. After a lot of experiments I settled for 840/230 which produces 352 MH/s each. Increasing ram speed decreases performance (oddly enough), and increasing core speed does *not* increase performance (even more strange).
Also they do not allow me to change ram speed on the fly *at all*. For each change in ram speed I needed to re-flash the cards. During the experiments I also noticed that contrary to my other cards the XFX 6950s will not lock up the system if they get to hot. They will pause for a moment, then restart. (I would not recommend running them like that, it happens at like 102°C) |