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Author Topic: Risk of damage from extreme memory underclock on 6990?  (Read 1408 times)
MiningBuddy
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July 29, 2011, 01:25:53 PM
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I flashed the bios on my 6990 with RBE after getting totally pissed with aticonfig and 11.6 drivers not actually adhering to the clocks I set.
I set the memory clock limit to 150mhz though aticonfig will still only allow me to clock 125mhz lower then my core clock, if I go past 125mhz difference the clock lowers down to my 150mhz limit, which is pretty good for me because it saves me almost 150w of power and around 10C temperature.
I am wondering though whether this can/will cause any damage to my card? I've had it run stable for around 3 hours and then decided to increase the clock until I get confirmation from someone more knowledgeable then myself.

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July 29, 2011, 01:44:47 PM
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The memory and GPU clocks are wholly independent, functionally and physically..  which makes it a real PITA that the mem clocks don't behave in linux. 

You can't hurt the card by tuning down the memory, however going too low may cause it to act a little weird.  Don't flash any values you're not comfortable with.

If you've got a Windows box handy it can live in for a couple of days, you should try to find your GPU / memory clock sweet-spot (where you get the most MH at comfortable temperatures and low memory clocks), then flash those settings for permanence.  After that you don't even need to mess with the clocks back in linux-land, it'll boot up where you want it.

I have noticed that a card flashed with lower clocks, when modified with aticonfig will fall back into the gpu - 125mhz bug regardless of the BIOS settings.


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July 30, 2011, 11:31:56 PM
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So are you saying that you run your 6990s at 150 memory now? impressive if so!

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August 11, 2011, 09:42:22 PM
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So are you saying that you run your 6990s at 150 memory now? impressive if so!
Not any more, they were stable for the 3 hours or so that I tested them and I raised the clocks to 600 just in case. I ran them again a few days later when we had some really hot weather at 150 for around 7 hours per day for 4 days and they seemed to be ok.
Something is nagging in the back of my mind about running them at 150 though and it makes me feel uneasy.

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August 12, 2011, 05:22:35 AM
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What about just running them at core speed/3 + 14 = your memory speed?

i wouldn't worry about the lower memory speed.  I just don't see how it could be "bad" maybe someone can explain if it is... but to my knowledge it's fine...

I should really flash my 6990s then...  sick of running 930/840.  want something more like 1000/300...

10 degree drop is quite significant.  less power draw is also fantastic. really improves the Mhashes/J for the card.

I'm surprised there's very little chatter about flashing 6990s.  Seems that those who run them, just live with the high memory clock speeds...

Where would I start to flash mine?

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