Wondering How do I underclock my 6990video memory under Ubuntu

[yyduinihao0]

Hi guys:

Today I just installed everything in Ubuntu. I get everything figured out besides "the way to underclock my 6990 video memory"
So,please help if you know the answer.
Also, I am wonder what is the lowest safe video memory clock? 300?

Thanks a lot!

[yyduinihao0]

Hi guys:

Today I just installed everything in Ubuntu. I get everything figured out besides "the way to underclock my 6990 video memory"
So,please help if you know the answer.
Also, I am wonder what is the lowest safe video memory clock? 300?

Thanks a lot!

300 is a good number, you can always tweak it a little afterwards. You want the tool AMDOverdriveCtrl. That'll lower everything below it's limit, but never above. For that you need to flash your GPU BIOS.

Thanks a lot for the quick reply.
However, today is the first time I use Ubuntu. So, can you provide me a thread about how to setup and use this tool?

[martok]

I don't know of a way to underclock a 6990's memory under Linux as yet. amdoverdrivectrl will lower the minimum memory clock but if you look at it in aticonfig, current will still be at 1250 even though target is set to 300.

[yyduinihao0]

I don't know of a way to underclock a 6990's memory under Linux as yet. amdoverdrivectrl will lower the minimum memory clock but if you look at it in aticonfig, current will still be at 1250 even though target is set to 300.

I actually tried the amdoverdrivectrl and it actually worked, besides it only allow me to sell the clock speed for my first GPU. the rest 3 can not be changed.

[martok]

I don't know of a way to underclock a 6990's memory under Linux as yet. amdoverdrivectrl will lower the minimum memory clock but if you look at it in aticonfig, current will still be at 1250 even though target is set to 300.

I actually tried the amdoverdrivectrl and it actually worked, besides it only allow me to sell the clock speed for my first GPU. the rest 3 can not be changed.

Did you use the -i option. On my rig, the gpus on the 6990 have ids 0 and 4 so -i 0 works then -i 4 also..

[darkpandora]

did you underclock your 6990 memory?

[molecular]

I don't know of a way to underclock a 6990's memory under Linux as yet. amdoverdrivectrl will lower the minimum memory clock but if you look at it in aticonfig, current will still be at 1250 even though target is set to 300.

I'm wondering this, too. The card just seems to ignore the "Peak Clock" setting and use "Current Clock" above that anyhow. What good is this?

I hope someone finds a solution.

[molecular]

did you underclock your 6990 memory?

aha! just found some info in another post: https://forum.bitcoin.org/index.php?topic=18107.msg229587#msg229587

apparently you can underclock ram down to 100Mhz below core clock.

[qed]

did you underclock your 6990 memory?

aha! just found some info in another post: https://forum.bitcoin.org/index.php?topic=18107.msg229587#msg229587

apparently you can underclock ram down to 100Mhz below core clock.

Under linux? Under windows that's not true.

[molecular]

did you underclock your 6990 memory?

aha! just found some info in another post: https://forum.bitcoin.org/index.php?topic=18107.msg229587#msg229587

apparently you can underclock ram down to 100Mhz below core clock.

Under linux? Under windows that's not true.

What do you mean? Can you underclock more than 100 Mhz below the GPU clock or can you not underclock at all (meaning that you can set the value but it wont be honored)?

[qed]

did you underclock your 6990 memory?

aha! just found some info in another post: https://forum.bitcoin.org/index.php?topic=18107.msg229587#msg229587

apparently you can underclock ram down to 100Mhz below core clock.

Under linux? Under windows that's not true.

What do you mean? Can you underclock more than 100 Mhz below the GPU clock or can you not underclock at all (meaning that you can set the value but it wont be honored)?

Under windows the lower memory limit is 625MHz if using "normal" methods, not related to the cpu clock.

[liuk03]

did you underclock your 6990 memory?

aha! just found some info in another post: https://forum.bitcoin.org/index.php?topic=18107.msg229587#msg229587

apparently you can underclock ram down to 100Mhz below core clock.

Under linux? Under windows that's not true.

What do you mean? Can you underclock more than 100 Mhz below the GPU clock or can you not underclock at all (meaning that you can set the value but it wont be honored)?

Under windows the lower memory limit is 625MHz if using "normal" methods, not related to the cpu clock.

i'm trying to set the memory clock of my 6990 but with MSIafterburner on w7 the lower memory limit is 779..if i try to set the value under this limit the clock go automatically at default value 1250MHz, why this?how i can put down this limit?

[martok]

So it appears these other posts can be applied to the Linux situation as well. The current state is that the 6990 doesn't honour the memclock set with amdoverdrivectrl at 300. However, I can underclock mine as low as 755 using amdoverdrivectl and it will be honoured. Any lower and the clock jumps back to 1250. But 755 is certainly better than nothing.

[kloinko1n]

So it appears these other posts can be applied to the Linux situation as well. The current state is that the 6990 doesn't honour the memclock set with amdoverdrivectrl at 300. However, I can underclock mine as low as 755 using amdoverdrivectl and it will be honoured. Any lower and the clock jumps back to 1250. But 755 is certainly better than nothing.

Mine are set to 500 for the adapter that also handles the graphics for the monitor, and 450 for the other (3) adapters. If you play with the voltage (lower it *a bit* in AMDOverdriveCtrl), maybe you can get also in that region. I think that would lower heat production significantly.
But I'm not sure about your situation, because due to cooling issues I have to limit the core clocks significantly: 500 MHz @ 75 deg C @ fan speed 65%.
Voltage I think I put at 1.090 V.