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I know reducing the clock speed of your GPU memory can save power, but does it also effect the thermal properties of the card?  Meaning, if I underclock the memory of the GPU, will the GPU run cooler?

Thanks!

yes, and it will hash faster too.  :o

this. My 5830's are set a 980/300/1.16v/78C and getting 315 Mh/S using Trixx

Not always, I clocked mine to around 600mhz, and I got some very low mh/s, then I changed it to around 850mhz and I mine at 220mh/s from one card..

thats because you didn't clock your memory down to 300mhz. its a magic number, try it.

Think about it.. what heats your card? Electric power. The less power it draws, the less it will heat up. The memory controller is on the GPU, and much of the savings come from there, its not only in the RAM chips. So yes, the GPU will run less hot by a few degrees at least.

thats pretty interesting, i would suggest we create a table similar to the mining_hardware one -- with underclock ratings for all the cards & best found values, flags used, o/c used etc etc

i would also love to find a definitive list of all the various flags for use in poclbm, cgminer, diablo, etc

Someone already made a chart of that, but Ill damned if I can find it. IIRC the bottom line was that ~200-400 MHz was the sweetspot, performance tapering off slightly in either direction

It depends on your card my 4850 would crash below 450mhz and the 6770 I had let me get down to 300 the lower it is the cooler your card will run

i found a chart but it only showed that 300mhz was the spot & only for one card.
i was thinking a table with many cards & values..
http://smpake.com/data/img/5770mem.png

Thats already a useful chart, but not the one Ive seen.
I dont think it will be very different for other cards; afaik all popular mining cards use the same basic shader architecture, so I would expect very similar results.

I usually set mine for 333 MHz on a 5870 !

157

Actually, for me there's only a tiny difference between a high memory clock and 300mhz (though with the higher clock, I get like 2 or 3 extra mh/s). But it would be better to keep at at around 300mhz, as others have said, it lowers your temps slightly and might even increase your mhash!

That is only for 5870s and 5xxx series mostly. I think the 6xxx series can only go down to 900 mhz on the memory.

Is 300Mhz ideal memory speed for a 5830 as well?

Yeah. Its the same chip as the 5870 and 5850 just with some parts fused off.

I drop a few degrees C by underclocking my memory. 

360Mhz is the sweet spot for my 3 5870's

Interesting.  I just downloaded trixx and I like it more than the AMD VISION OC.

What flags/software are you using to get 315Mh/S, what OS (windows/linux), and what's your fan speed (%)?

I turn mine down all the way to 300 on my 5830's.

I got down to 150Mhz on my 5970s. But it seems to cost a bit of performance, so I tuned them back to 300 Mhz. Not much difference in power consumption anyway

7970 is core 925/ mem 700 / volt1068

Does anybody know the best mem speed for 6870's? My 5830's get 330mhash @ 1000/300 but my 6780's crash any time I play with lower memory speed.

Hello
I tried to lower at 300mhz and the selected card turned itself off  :o  (holy crap!, I almost shit myself thinking that i had fried the card) the other card was still runing, powercycle and everything go back to normal.

If I lower to 500 mhz, it still works, same performance, but i start to se some crap on the screen from time to time (artifacts).

runing memory at 600mhz is stable.

I have two HD 7850 Sapphire 1GDDR5, with the GPU at 700Mhz (default is 860Mhz) I get 205Mh/s per card, it's kinda slow but I'm concern on frying the card if I push it at max speed for long periods of time, what do you think?

Default voltage is 1138, I lowered to 1130 but not sure what is convenient, I am more concerned to keep the board safe than to get more performance out of it.
Temperature is 59 C (with 27 C ambient) in both cards. (fans are in automatic at 50% PWM)