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Title: unable to downclock memory on 6870 Post by: perryh on May 25, 2011, 12:18:19 PM Hi
I have a ref board 6870 and I can't downclock it in linux (ubuntu) I am using AMDOverDriveCtrl and I have successfully adjusted the 3 profiles to run the memory at 400mhz, but the info tab still displays that the memory is running at 1050mhz under load. Before I run the miner, it successfully changes my memory's clock to 400mhz... but it goes up to 1050 right after. Any ideas? Thanks -perry Title: Re: unable to downclock memory on 6870 Post by: perryh on May 25, 2011, 06:32:10 PM up
Title: Re: unable to downclock memory on 6870 Post by: a7thson on May 25, 2011, 06:53:08 PM Before I run the miner, it successfully changes my memory's clock to 400mhz... but it goes up to 1050 right after. Sapphire 6870 here -- Same issue and same behavior. I had hoped there was a way to avoid using the Radeon BIOS editor but that's probably the next step. Sadly, my setup is a linux box, so I'll have to dig up an XP boot cd or try FreeDOS, I suppose, to do the deed. Title: Re: unable to downclock memory on 6870 Post by: a7thson on May 25, 2011, 11:09:29 PM Any ideas? This seems to somewhat address the issues. Unfortunately I don't have an MS Windows setup so the recommendation to use MSI's Afterburner is probably next to useless for me. http://forum.bitcoin.org/index.php?topic=9652.0 This longer thread also addresses underclocking more generally, though again everything is Windows-centric >:( http://forum.bitcoin.org/index.php?topic=4292.0 Maybe they'll help you... I seem to be out of options. aticonfig --adapter=0 --odsc 0,350 fails with: ERROR - Set clocks failed for Adapter 0 - AMD Radeon HD 6800 Series Please check that input values were valid But succeeds if that application (AMDOverdriveCtrl) is running. However, even though the "peak" values can then be changed accordingly, the actual clock speeds never move, even if all the profiles are set with the lower clock speed. Moreover, once I exit AMDOverdriveCtrl, it restores my old settings with the default 1050Mhz memory clock. It's beyond annoying. Title: Re: unable to downclock memory on 6870 Post by: Pygy on May 26, 2011, 02:08:09 PM Save the profile, and edit it by hand in a text editor (mine is called mem300.ovdr)
Code: ("$ nano mem300.ovdr ") <?xml version="1.0" encoding="utf-8"?> You must change the mem param of the performance levels 1 and 2 to 30000. Then you can load the profile from the command line with Code: $ AMDOverdriveCtrl -i N -b mem300.ovdr Code: $ AMDOverdriveCtrl -h However, I don't know (yet) how to adapt the voltage for these lower memory clock rates... Amazingly, lowering the memory clock increased the hash rate from ~320 to ~325 MH/s Title: Re: unable to downclock memory on 6870 Post by: TurdHurdur on May 26, 2011, 02:12:51 PM There's always 100 less than the core clock, at least.
Title: Re: unable to downclock memory on 6870 Post by: Pygy on May 26, 2011, 02:36:21 PM There's always 100 less than the core clock, at least. I'm sorry, but I don't understand your reply... Title: Re: unable to downclock memory on 6870 Post by: TurdHurdur on May 26, 2011, 03:09:14 PM There's always 100 less than the core clock, at least. I'm sorry, but I don't understand your reply... Title: Re: unable to downclock memory on 6870 Post by: picollo7 on May 26, 2011, 05:07:58 PM Same issue here. The lowest I can downclock it to is 850. I think it has something to do with the voltages. If you look at the voltages, it the mem clock speed is 300 at 1, and then goes to like 950 at 1.17. So I think it is just a limitation of the card due to the voltage changes. 850 is the lowest I can go at 1.17.
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