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Author Topic: Under-rated?  (Read 4694 times)
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July 15, 2011, 04:43:20 PM

Just broke two fan blades on a 6950 . Much louder but still workin fine.
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July 15, 2011, 05:00:14 PM

Is there a way to set the card up with those clocks under Linux?  Aticonfig won't let me go outside the defined ranges of 500-840 and 1250-1325 for core and memory respectively.

I can see where cranking the clock that high would get more Mh/s.  Similarly, lowering the memory speed would allow the chip to run a bit cooler.

I'm still trying to figure out the optimal settings for core and memory.  Dropping either one lowers speed and heat.  Seems like core has a bigger impact on speed and memory a bigger impact on heat, but I'm basing that on what I'm reading in forums like this, not from any empirical testing.

You have to edit the bios with RBE to adjust the ranges. Since I use my cards only for mining I just changed all the memory clocks to 300. I changed the core clock to 900 and I did not see any improvement in MH/s. aticonfig would show the edited core clock, but I'm thinking since I couldn't change the voltage the core can't get enough power...

Even tried editing the registers via RBE to attempt to overvolt, aticonfig would still only show stock voltage.

btw, this is with a reference card, shaders unlocked.
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July 17, 2011, 04:03:18 AM

Well, the thing about these cards that I find annoying

Annoying yes, but well worth it if you get them working properly. The worst issue right now is that there can't be more than a 125 Mhz delta between the core and memory clocks. Pushing the mem clock down from 810/1250 to 810/685 brought the temperature down by over 10C, so the memory is definitely a problem there. Other than that, they're good cards.

I'm using 2x6950 Asus DCUII 1Gb cards; both are set to 850/725 @ 80% fan speed using the following:

atitweak --set-engine-clock=850 --set-memory-clock=725 --set-fan-speed=80

You can also use aticonfig, I've just come to like atitweak.

aticonfig --adapter=all --odsc 850,725

The cards are currently 68C and 71C with no case and only a weak box fan that does a lousy job clearing heated air from the dead space between the cards. Dropping fan speeds down to 60% brings temperatures to 72-76C and 50% goes to 75-78C.

Currently running Catalyst 11.6/APP 2.4SDK and Phoenix 1.50 using the latest phatk kernel with options "VECTORS BFI_INT AGGRESSION=12". They're pushing ~345 MH/s with those settings. During cooler times of day, they get kicked up to 880/755 @ 80% which gives ~360 MH/s and temps of 70-74C.

I have yet to attempt flashing the BIOS or changing voltage. Even with all else being stock, I can push them to about 920 Mhz and brush up against 400 MH/s, although the temp gets into the 80s and they aren't completely stable. With voltage control and the ability to underclock mem more than 125 Mhz below core, I'm fairly confident I could approach 1 Ghz and easily exceed 400 MH/s while still keeping the temp around 85C or below.

It's tempting, but I don't want to install Windows (outside of a VM to run RBE) to make those gains. I'll be testing Hashkill soon to see if that offers any improvement. Otherwise BIOS flashing seems to be in order - and maybe some Arctic Silver. At least that can be done with a FreeDOS USB drive and a screwdriver.
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