Topic: heads up: HD6xxx memory does NOT actually underclock (Read 4519 times)

I have a Asus 6950 DC2 1GB and I noticed the memory doesnt under clock correctly when trying to use programs such as afterburner and so forth. But ati tray tools allows me to take the memory all the way down to 150mhz or lower...and confirmed it w/ gpuz sensors and power usage substantially dropped.

Eh I'm pretty sure clock speeds aren't going to brick your card. Voltage and heat will do it.

That being said, I put together my 3x 6950 setup with linuxcoin and ran into the same problem. I couldn't get the memory to clock under core - 100. I disabled CCC Overdrive and it didn't help. People said Catalyst 11.6 fixed that (maybe it did with 5000 series cards) but it didn't do me any good.

The only guys who seemed to be getting anywhere were the ones who flashed the bios to another manufacturers (I think Asus) or modifying the bios to change the min/max speeds.

http://forum.bitcoin.org/index.php?topic=19776.msg290674#msg290674

Win 7, but if win can do it its not the card's fault.

As for why I advise against it, see http://forum.bitcoin.org/index.php?topic=31584.0 

i have no idea what you mean. how are you underclocking memory for a 69xx series on linux and why do you advise against it?

It underclocks just fine. Unlock AB, it will stick at any number. Id advise against it though...

So you don't know how to do what this guy did either?

Lots of Linux overclocking info here:
http://www.linuxcoin.co.uk/wiki/index.php/Overclocking

I've got two 6970's and was able to get their mem clocks down to 755.  Any lower and it would shoot up to max when under load.

Not a problem!

I have 3x 6950's coming here on Monday/Tuesday and I'll be running linuxcoin on this box. Ill let you know if run into a similar issue.

Thank you you heaps for taking the time to do that! You are totally right. Now if the 'disable AMD overdrive' dude is correct, I just have to figure out how to do this under Linux and maybe my gf and my power company will hate me a little less.

The reason why you can't lower the memory clocks is because you have to disable AMD Overdrive in CCC.  The problem is that the 69xx series need Power Control Settings set to 20% for optimal performance.  Some cards can bypass this (ex: MSI 6970 Lightning) but others cannot unless AMD Overdrive is enabled.

Same experience here - XFX 6870 (the reference design). Can "try" to underclock both in afterburner or TriXX, but the actual frequency is still high..

Ran a test.. I don't think I need to run it very long at all. The temperature difference was immediate. I waited until things stabilized then took some screenshots/pics of kill-a-watt. Here are my results. (Also, these cards are Sapphire http://www.newegg.com/Product/Product.aspx?Item=N82E16814102921)


Underclocked memory results:
https://i.imgur.com/X6mYk.jpg

Default memory results:
https://i.imgur.com/gBEJT.jpg

sapphire

Well, I read your thread title and your first post, you seemed to imply that this was true for all 6xxx cards.

It was supposed to prove that all videocards are capable of clocking down to 150 mhz at the very least.

All I can say is that I have 6870 from MSI and 6950 from Sapphire. All of them underclock.
If this is indeed some hardware lock or bios lock, maybe the people who have this problem should post which vendors have this issue.

So which company is your problematic cards from? XFX? HIS? Asus? or?

so are you suggesting that it's a bug in both GPU-Z and afterburner sensors? because in my screenshot, they both agree with each other, so i doubt they're both wrong.

it seems like it's a hit or miss with the cards you get. from what i've seen so far, there has been more people unable to underclock the memory to the 300mhz range than people that have successfully done it. just like with flashing a 6950, not all of them are flashable because they're hardware locked. and the ones that could be flashed, not all of them are able to unlock extra shaders to a 6970. it's just the luck of draw, but you make it seem like anyone not being able to underclock the memory is really that incompetent. it's pretty straight forward to do, no? just like with the HD5xxx series, all you do is pull the memory slider lower or enter values in small increments. however, on all the ones i've tried, it just reverts back to default memory clocks. this was done on all updated software versions and verified with different sensors. i looked at the power consumption and temps, and it indeeds corresponds to stock memory speeds.

btw, your link to legitreviews.com proves nothing. ya sure the core and memory underclocks iteself when idle, but once you put a load on it, they both default back to normal clocks. that article did NOT manually  test a memory underclock at load like you said. you should try reading that article yourself before making a reference to it.

ok, but if they were underclocked I'm fairly sure you be a bit cooler. Try a test - as is, then back to max. Run max for a few hours, post the two temp diffs. I'll be really interested in your answer since I haven't been able to uc mem very far before it reverts to max.

Yeah, the case is closed (with 2x120mm fans on the side) in my basement which is about 85F ambient right now (I live in PA, hella heat wave!)

Usually they sit lower than that

and your temps are still 72? Mine are 69 for a 6970 at 880/780. It doesn't really look like that underclocking is working to me.

I was having the same problem.  I flashed the bios to lower the maximum clock to where I wanted and now it works fine.