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Under-rated?

your fine on 800 watt system with two 6950s overclocked. I ran 3 6950s on a 850 watt power supply. I think ATI has been selling more 6950s on average than the 6970s. I have one 6950 with shaders unlocked gets about 355 mh/s and one with locked shaders gets about 333 mh/s so shaders matter imo. The only other differences between the cards is supposedly the 6970s have slightly better memory (not relevant to mining) they have a 6+8 pin power inputs and can draw more power from the PSU, which despite the extra power draw I can't find much difference in performance. The 6970s arguably have better cores for overclocking and can hit 1 ghz easier probably than a 6950 can. However I think if you can get your hands on an unlockable 6950 the price difference isnt worth it for a 6970 imo.

Depending on the 6950 you get, with overclocking the gpu and underclocking the memory you can get 400Mh/s.

My XFX 6950 with stock bios/unlocked shaders is currently running at 910/625 at 1.175V and I get ~401Mh/s

So, yeah, the 6950's are nice cards.  ;)

my i5 2500k with 4x 6950 1gb pulls 820watts from the wall, using a 1200watt psu.

so guessing a good quality 750watt should be fine for you.

The "minimum requirements" for a 6950 is a 500Watt power supply... they pull about 169 Watts @ load with stock settings.  I'm running an XFX 6950 @ stock and netting 318Mh/s with a Corsair 600 Watt PS with zero problems.  I wouldn't be scared to add a second card if it had the extra PCI-E connectors.

I question that 8% variance though... the 6970 has more shaders and a higher clock speed... you might be comparing the 6950's with unlocked shaders.  Those cards are getting a little harder to find.... my XFX has a locked bios and I may not be able to unlock those extra shaders (people have been having a 50/50 chance on this particular board revision).

If you do have unlockable 6950's though, you basically already have 6970's.

too right they are under rated ! im getting about 400 mh/s each out of my two ! well good !
my 600 watt ocz power supply cut out when i added the second card, so i bought another 850watt one and all
is good  8)

I'm running two overclocked 6950's on a 5 year old 750 watt PC Power and Cooling PSU.  You might be able to go even less wattage, considering that in addition to the cards I'm running an overclocked i7, six hard drives, two optical drives, a sound card, a USB PCI card, and seven case fans.

That said, I wouldn't recommend going less than 600 watts for two 6950's in an otherwise bare-bones system.  1000 watts should be more than enough for three 6950's.

I'm running a couple rigs with 2x 1GB XFX 6950s - shaders aren't unlockable on any of them unfortunately, but at 885/760 gpu/mem clocks I get 345mhash/s each.  Sempron single-core 45W CPU and cheap g-skill ram.

Each rig pulls ~410W at the wall.  1000W is lmao.  I got a nice 750W 80+ Corsair PSU expecting more draw, but even adding a third card I won't hit that limit.

What do you guys think about a 450 or 500 run of the mill power supply for a single 6950? I just bought an ASUS EAH6950 from amazon and didn't think about needing more power for just one card.

For 1 x 6950 it will be fine. I run 2 x 6950's on a 700W.

For your reference: I run 3 x 6950s (adding a 5850 soon) on a 1250 PSU (80+ Gold) and they only draw ~630-640 W.  The cards are non-reference, so I can't unlock the shaders  >:( but with CCC overclocking, I can hit 1 GH/s intermittently (which jives with previous posts). 

I have run 1 6950 on a very old, but nice,  450 W PSU and am currently running 2 on a 600 W PSU

I snagged a nice "open box" MSI R6950-2PM2D2GD5 Radeon HD 6950, which is a reference card, on newegg today. I expect I'll flash it to a 6970 and add it to my miner. That will then be a GPU line-up of 6950 (flashed), 5850, and a 5830. All runing on a OCZ EliteXStream OCZ800EXS-B 800W PSU. Should be fine. If not I'll swap out the Tagan 900W PSU from my gaming maching which requires nowhere near that much PSU.

I've got 7 of those cards. You should just unlock the shaders and not flash the 6970 bios. You should see around 360MH/s once you unlock the shaders. Good luck with overclock, I am unable to increase the core voltage since I run linux and just upping the core speed didn't change my hash rate.

--
BigBeerJR

I have 15 xfx 6950's was lucky on 5 of them to be version 2 and unlocked them, I tryed 11.6 drivers with no luck, what drivers do you think are best?

MSI R6950-2PM2D2GD5 's can do 430 mh/s easy.
voltage 1200
core clock 970
mem clock 800
fan at 75
shaders unlocked.
good air movement around the cards. conditioned air that is.
using pocblm whatever with phatk kernel.. making sure it has all the lastest code tweaks.

and that is not pushing it to the max. i used to run 980 core clock but decided to take it a bit easier on the cards
and get excellent stability at a temp of ~54

the 6950 reference cards at a price of 250 are an excellent deal for mining and gaming.
but with the difficulty going up it will be hard to pay them off now days at a fast rate.
they had a rebate too just a while back.. but be careful you are limited to one rebate per household.

oh.. and be careful buying refurb cards. i bought a 5970 refurb and as soon as i pushed it
the 2nd core on it started giving me problems. it was obviously still bad in some way and i returned
it for a refund.. thank goodness. buying new or seeing it in action before you buy is probably the way
to go unless you can return it no questions asked.

How are you changing the voltage?

I like my 6950's, but I cannot over clock them past 900, even at that the machine will lock up after a while, so I run them at 875 core, mem 310.

I tried to flash them to a 6970, but apparently that hard wired the locked out shaders.  there is some instructions on the internet on how to open the card and connect 2 pins of one of the icchips, but I am reluctant to do that.  I get about 345 Mhash with them with a solid share acceptance rate.

they run a little hot, but that might be because I am also using them as bug zappers here in the shed :)

I though unlocking the shaders required flashing to a 6970 BIOS? I'd be very interested to hear your method.

If you download RBE you can simply dump the stock bios via atiflash, open it in RBE and then only unlock the shaders. Afterwards you can flash the modified bios back to the card. On some of the OC boards people don't recommend the 6970 bios because it changes too many timings/etc.

Sounds resonable. Is there a code listing of the stock 6950 BIOS you can point me to that shows exactly what lines to modify? I don't want to screw it up just mucking around ;-)

I am actually NOT a fan of the 6950s.  I run a mix of:

5770s
5830s
5870s
6870s
6950s

The 6950s run hottest of all and are the biggest pain to OC (in terms of getting them up to max temp of 72C while still getting some benefit from overclocking.  I'll be selling mine after I replace the slower cards in my mix.

For me, I can't even see the benefit to unlocking the shaders as that would just give me the "possibility" of more overclocking.  As it is, I can't clock any of them to max speed without overheating.  They typically run from 75% to 90% of their max overclock depending on time of day / room temp.

What 6950s do you have? I have 2 x ASUS EAH6950 DCII/2DI4S/1GD5 that get 380MH/s at 72c. Here are my settings if it helps you:
930MHz clock
625mhz clock memory
65% fan manual set
poclbm through guiminer with -v -w128 -f10
Mine were running high temps with an older driver. Make sure that you use the newest 11.6 available from ati/amd.

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.

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.

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

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.

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.

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

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

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...

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.

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

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

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.

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.

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

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.

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.

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!

MOAR HASH!!! :P 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.

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

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.

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.