Hi, I'm new to the Bitcoin community. I started last week, and I thought I'd share my experience with optimizing performance on my 6950 under Windows. I'm currently getting 324 Mhash.
USE THEM ON YOUR OWN RISK. I TAKE NO RESPONSIBILITY FOR ANY DAMAGE ANY OF MY SUGGESTIONS MAY CAUSE. But then I'm fairly anonymous and in a country where they would just laugh at you if you tried...General tipsOverclocking
(potentially dangerous to your card, use with caution)
Get MSI Afterburner
. Install it, then open the file MSIAfterburner.cfg in the Afterburner directory in notepad. If you use Windows 7 and possibly some other versions, you need to run notepad as Administrator, otherwise you will not be allowed to save it.
Make sure the ATIADLHAL looks exactly like this:
EnableUnofficialOverclocking = 1
UnofficialOverclockingEULA = I confirm that I am aware of unofficial overclocking limitations and fully understand that MSI will not provide me any support on it
UnofficialOverclockingMode = 2
AccessibilityCheckingPeriod = 0
This will allow you to overclock the card more than specified by the driver. It will also allow you to control the fan, which is important to keep the temperature down. I prefer staying under 80C.
The normal frequency on my card is 800 MHz on CPU and 1250 MHz on memory. For mining you want the CPU to be as high as possible. Memory on the other hand is hardly used at all, so it should be low to avoid adding unnecessary heat and power consumption. My current speed is 890/500, giving about 324 Mhash. It seems to work at 900 but crashes at 910, so I give it a bit extra headroom.
You need to figure out how much your card can take on your own. Do small increments (5-10 MHz) and let it run for a few minutes. Eventually it will freeze your computer, which means you've reached your limit. Back down 15-20 MHz and keep it there.poclbm parameters
Just -w 64 without -v gives the best performance with my 6950.6950 specific
I do not recommend using the 6970 firmware. Instead use your original firmware, but modified with the "shaders unlock" patch. There have been several reports of permanent damage, probably because of the different voltage and timings used in the 6970 firmware. It will also make the card use more power, which means higher cost and quite a lot more noise from the fan.
To patch, download these files:http://www.techpowerup.com/downloads/1920/HD_6950_to_HD_6970_Flashing_Tools.htmlhttp://www.techpowerup.com/wizzard/Mod_BIOS_HD_6950.zip
Unpack both them and download this file: http://pastebin.com/fLTmqWby
and save it as flash_to_6950mod.bat to the same directory (flash_to_6970.bat, flash_to_6950mod.bat and run.bat should be in the same directory). Then run flash_to_6950mod.bat. You need to run it as administrator, at least under Windows 7. What this does is save your current firmware, modify a copy of it, and then flash it back.
After flashing the first time you should make a backup of the directory, to make sure you can flash back the original firmware if you need to. If you like you can also try flashing to 6970 using the appropriately named .bat file. If you want your original firmware back you run flash_back_to_6950.bat.
At 890 MHz I actually get slightly higher performance using the 6950 modded firmware compared 6970 firmware, and to keep it under 80C the fan only needs to spin at 36% instead of 46%. My guess is that the 6970 firmware makes the card uses more power than it can supply, and starts throttling.
Flashing the modded firmware is pretty safe because the card has two firmwares, one of them read only. If your card stops working after flashing turn it off, flip the switch on the card and reboot. When it has booted and is running, flip it back to 1 and flash back your original firmware.