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And it did nothing. My hash rate didn't change. My temps didn't change. I don't understand why this is recommended.

Hashrate improvement is hit or miss and will require you finding your sweet spot usually between 300 and 400. But, if you dropped your mem core down that much and didn't notice a temp change... are you sure you actually dropped it? But even if you did, it will at least reduce power consumption.

This is what works for me

Memory clock = (core clock / 3) + 14

I lowered my memory clock to 300 in Trixx and it crashed my computer. It never used to do this, so I'm not sure what is going on.

Do you have a 5830? I am unable to bring down the memory clocks on my 5830's but I can do it with my 5850's.

I think I lowered the temp on my 5870@960 about 6-8 degrees when I dropped the memory speed to under 400. It also caused my PSU to slow its fan down to the lowest setting (Corsair HX750, which should indicate less than 40%/300W system load if the circuit is true to the graph in the PSU spec)

It did give me a few too many system lockups though (probably because it's a non-dedicated miner on Win7 with Aero and everything), but it's nice and stable and still a few degrees cooler with memory at 600.

My system is stable and all at 300...I just don't see what the point is.

It varies where the sweetpoint is. For me 759 works as good as ~300-400(-4 temps, default 1250). When going little away from 759, it raises the temps back to normal.

I did have trouble getting it to low ~300. When I pressed apply, it actually didn't change anything. As many ~new cards have 3 profile steps, "idle" "med" "high". Usually the programs only change "high". But when you underclock below "med" values, it might not change anything. So I had to downclock "med" values before I could go as low as 300Mhz memory.

Maybe these profiles are the cause of crashes...

higher is always better

Psh if your referring to the mem clock, Then thats Only for nvidia

You use less power which in turn saves you money.

No, I have a 5850, I just think Trixx is buggy.

I started Trixx up once and it was set to 725, 4000, and 1200 for the three settings, the Memory clock seems to vary widely. Plus, it doesn't help that when I click to move between the entries it clears them so I am never certain what I am setting them to when I click "Apply".

I'm wondering if maybe there's a better overclocking program I'm missing out on. Also, how hot is too hot to run these cards? I never really hear anyone commenting, but I've heard some people were going as high as 80 to 90 degrees Celsius, that seems awfully hot...

MSI Afterburner works for me. Also, I have had my Gigabyte 5850's running as hot as 99 degrees Celsius without failure.

If you use phoenix, it should help if you downclock memory. Just change worksize from 128 to 256 for the downclocked card(s), otherwise the difference seems small.

At least improved my hashing rate on all cards (5850 & 3x 5870) by some 10-15MH/s. Didn't really see a measurable decrease in temps, but afaik some people have reported some 15W drop on power usage.

On a 4x 5830 system we got about an 80W decrease in power usage by going from 1000Mhz to 250Mhz.

Some cards behave differently, but every 5830 I've DC'ed the memory has used less power, run cooler and slightly improved hash rate!