Quote from: jgraham on June 27, 2011, 07:08:05 PM

Quote from: darkpandora on June 27, 2011, 04:05:04 PM

Quote from: jgraham on June 27, 2011, 02:55:28 PM

Did you try with the latest drivers?

Catalyst 11.6 seems to have the restriction removed (you don't even need amdoverdrivectrl)

Adapter 0 - AMD Radeon HD 6990
                            Core (MHz)    Memory (MHz)
           Current Clocks :    955           1250
             Current Peak :    955           800
  Configurable Peak Range : [500-1200]     [1250-1500]
                 GPU load :    0%

Adapter 1 - AMD Radeon HD 6990
                            Core (MHz)    Memory (MHz)
           Current Clocks :    955           1250
             Current Peak :    955           800
  Configurable Peak Range : [500-1200]     [1250-1500]
                 GPU load :    0%

you need amdoverdrivectrl i think.. look at your current clock and current pleak:)
Current Clocks : 955 1250
Current Peak : 955 800

You might be right, definitely one of those measurements is in error (since you can't have a current above your peak). Prior to the patch, if you attempted to set the memory clock below 1250 you would get an error and combining that with the fact that I wasn't able to hit 955 or 960 at 1250. I'm guessing that this is actually running at 800. I'll see if I can come up with a better test.

you can only set memory clock 100mhz under gpu core clock as i mentioned here:

Quote from: darkpandora on June 25, 2011, 02:29:34 PM

Quote from: FreeJAC on June 25, 2011, 01:51:51 PM

I don't think there is any advantage to overclock the mem. I would leave it the same or lower it anyway. OS shouldn't matter really, whatever is your personal preference is IMHO. If you do switch to Windows there are reports of some having difficulties getting that 4th card to show up. What mobo are you using?

my motherboard is MSI 890FXA-GD70.
the memory is not a problem, on 6990 you cannot downclock memory more then 100mhz under core speed (example: gpu 900 memory 800, gpu 970 memory 870). i think my problem is low voltage, on ubuntu amdoverdrivectrl the max voltage is 1.175.