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hi! i finally started mining with my 6950`s and i think what flags i should use with stock clocks?

GPUs: sapphire radeon HD 6950 @ stock settings

hash rate: ~295mh/s per card
temp: ~ 70 celsius with horrible fan speed (not have pc case at all)

GPUs are connected with crossfirebridge. and im not oc:ing or unclocking cards yet, but maybe i put that extra 20% power thing on in CCC.
i use guiminer @ btcguild

so can flags help to get little more hashrate with lower temperature? :)

Driver version? SDK version? Operating system? Miner?

There's a whole suite of miners and mining kernels, each with its own range of optimal settings like vectors, work size, aggression/intensity... unless you're more specific about your system configuration, I don't believe anyone can help you.

Crossfire is totally irrelevant for mining. Thermal management will be easier if you are able to remove the crossfire bridge and spread the GPUs farther apart.

Since you need uncomfortably high fan speeds already I discourage you in the strongest possible terms from increasing the powertune parameter.
Fanspeeds over 70% are not only unpleasant but detrimental to the fan MTBF. Running the GPU fan at 100% is a surefire way to destroy it in a couple of months.

Take your time and browse through Mining (https://bitcointalk.org/index.php?board=14.0) and its subforums.
The Pictures of your mining rigs (https://bitcointalk.org/index.php?topic=7216.0) topic might give you some good ideas about optimizing the airflow across the cards.

i use newest driver and SDK, windows 7 and GUIminer

more info:
cpu: intel i5 2500k
mobo: asrock extreme3 gen3
psu: xfx 850w 80+ bronze


why i cannot use crossfire with mining?

i have one comp with similar setup 2x 6950 flashed to 6970 and they run about 700 mhash with 78 deg at fan speed about 2500

I never said you cannot use crossfire, I merely said it won't increase your hash rate at all.
Moreover, spreading the GPUs further apart (if possible with your mobo) might drop the temperatures by a couple degrees.

GUIminer provides merely a graphical interface, which mining kernel do you use? Poclbm? Phoenix?

SDK 2.5 is the optimal version for VLIW-4 cards. The lastest drivers come with SDK 2.6.

you should be able to get higher megahash rates out of your 6950s

You should get at least 375Mhash out of a single 6950.

Don't need to crossfire the two.

Overclock the 6950's from the default 850 up to at least 880 (can't remember if a 6950 will be stable at 900), drop the VRAM clock down to ~600mhz, install the latest Diablominer, and away you go.

Edit: Regard Crossfire, you don't need to have the bridge installed; the mining software deals with each logical GPU itself, and the crossfire serves no purpose whatsoever.

i use cf-bridge cus i play games too. now i get 330mh/s @840-1250 clocks with low temps (added some extra fans). how i can downclock the memory in my cards??  i think it has bios lock..

my card: http://cdn.mos.techradar.com//Review%20images/TechRadar/Computing/Components/Sapphire%20Radeon%20HD%206950/Sapphire%20Radeon%20HD%206950%20main-380-75.jpg

 I use a utility available here on the forums called ClockTweak, that works well on 6k and below series cards.

 Beyond that, look into MSI Afterburner, which should allow you to underclock your vram lower than CCC.

 

If your using Guiminer.. I would use -v -w 128,,,,, add -f 60 if your using the desktop.....

That's what works best for me....

I agree with the above post, and you should unlock to 6970 if you can, right now I'm getting 400-410 mh/s with guiminer, flags are -v -128 -f1.   Card is overclocked to 930 men at 200 and power at 2
 Fan is at 65% running at 65 c. Very stable, surprisingly. I am using sapphire trixx to overclock and underclock Memory
Card is a sapphire 6950 reference and I've had no problems so far.  ::)

ill try that tomorrow. i use -v -f30 -w128 flags in guiminer.

i post results tomorrow :)      edit. should i use newest drivers and SDK ?

Do you read the replys?
Driver abouve 12.3 are not optimal for old cards i heard.

IMO 11.12 and lower are better for for the older cards... I have mostly 5800 series...

Use phoenix 2.2, oc to min 975/300. should get you around 390+