Topic: Under-rated? (Read 5303 times)

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:


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


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.

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.

Just broke two fan blades on a 6950 . Much louder but still workin fine.

MOAR HASH!!! I'll lower the vcore when I get my other cards in. 1.25v is probably overkill I haven't tuned it down yet, I just jacked it up to see what stable clocks I could get.

1.25V - your cards probably eat about 30% more power. try a 1.1V OC setting, would be much more efficient. your card could probably even pull the same my card does, 950MHz at 1.1V and 424Mhash/s. think about the environment and all the CO2 you're producing. gosh!

actually atiflash is probably the best way to flash and its a dos app. Just make a dos boot usb drive put atiflash and the modded bios on there.

We get ~360mh/s from each of our Sapphire 6950's with 875/300 overclock on risers alone they were around 80deg most of the time...after Arctic Silver MX-5 69.5-72deg (in my shop that is  ~85deg (F) all the time).  There is a box fan directly above them blowing down also.

All the other GPUs I have running all run fine at close to 99% of max core AND memory clocks.  They also all run at or below 72C. 

I guess that's the main reason I find these cards so annoying.  They really do require you to drop the memory clock as low as you can while still keeping as high a core clock as possible.  Lot's of monkeying.  Other cards are much more "plug and play" so to speak.

I'll have to try to unlock shaders on one of the cards and see how that works.  I run mostly Linux boxes for everything.  But I'm sure I have a HD with XP around somewhere.  Seems like you can't unlock shaders w/o various XP apps.  ;-(

Well, the thing about these cards that I find annoying

I'm getting 440 mh/s on my ref unlocked shader card. Its doing 990 mhz 1.25v on core and only at 71c. My non ref frozr II with locked shaders is only doing 350 mh/s 875 mhz 1.1v on core and is around 81c. I don't know why temps seem strange but thats what they are.

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.

the cards i am speaking of are reference 6950s... so maybe i should have stated that better.
and i am on windows. i did not feel like dorking around with linux. win 7 prof x64

I guess I should have asked if you were on windows or linux. I am unable to change the voltage on linux.

MSI afterburner will edit the voltage of the 6950's.  but how did/do you unlock the shaders.  I dont think it is possible with the newer cards.

msi afterburner with the allow overclocking config in it's config file. also using an asus 6950 bios with shaders
unlocked but don't quote me on that...

Roger that.  thxs.  then I am glad I did not try.  I am happy with my:

875 core/ 310mem 345Mhash bugzappers. 6 of them

That's not quite right, and that thread has not come up with a method to hard-mod shader unlock quite yet, but someone who's good at tracing the leads may be able to find the anomaly and 'bridge the gap' so to speak.

That thread only shows how to jumper the write-protected BIOS to allow you to flash, it's hit or miss whether or not you'll actually be able to unlock the shaders.

I was under the impression that there were 1 of 2 things preventing unlocking the newer cards (or possibly a combination of both).

1 - The flash chip is locked, preventing you from flashing a new bios to the card. This requires a simple hardware mod to fix.
2 - Parts of the PCB are actually laser cut to prevent access the the necessary circuity. If this is the case you even a bios flash will not unlock them.

I tried to do just that but:

this only works for the earlier cards...  they 'hard' locked the shaders now, requiring to open the card and connect two pins of a specific circut.



edit:  found the instruction on unlocking shaders for non-referenced xfx 6950's  http://forums.extremeoverclocking.com/showthread.php?t=355592

There is a php script floating around on the forum somewhere that will modify a saved bios file if you don't want to use RBE.... RBE has a checkbox to unlock the shaders.

Well, here's a snippet from one of my machines right now.  I forget the specific brand but they're similar to the one you reference:

Default Adapter - AMD Radeon HD 6900 Series
                            Core (MHz)    Memory (MHz)
           Current Clocks :    730           1297
             Current Peak :    730           1297
  Configurable Peak Range : [500-840]     [1250-1325]
                 GPU load :    99%

Default Adapter - AMD Radeon HD 6900 Series
                  Sensor 0: Temperature - 72.00 C
Fan speed query:
Query Index: 0, Speed in percent
Result: Fan Speed: 77%

It's cranking out 271 Mh/s right now.