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Just looking for some discussion on optimizing the 5870 and pushing it to its limit. I'll try and update my first post with really useful information for those running 5870's as well. Also looking for advice on mine.

My setup is is two 5870's. I'm using MSI Afterburner to configure both of my cards independently. To adjust voltages and lower memory speeds really low you have to edit the MSIafterburner.cfg file like so

I have one at 980MHz core 180MHz memory and 1.2v and another at 960MHz core 180MHz memory and 1.2v core. Temps stay bellow 80 depending on how much I crank up the fan.
My .bat file to start the latest phoenix miner using slush's pool looks like this.
I'm using CCC 11.4 and SDK 2.4.
Each card pulls ~400Mhash/s at these settings in windows 7. I have a Core i7 at 3.8GHz and 6GB DDR3 RAM.

What works best for you guys? Mine clearly isn't ideal and I need to adjust it, I'd also like some input on that..
I've heard using -f 1 or -f 0 can increase your output quite a bit, how's that work for everyone?
What voltages are people running at? I had a hard time getting this stable and went up to 1.2v, but I see people with a lot less. I can't even get my aggression above 7 atm, above that it is likely to crash. I've heard SDK 2.1 is the best, but how does it compare to 2.4? I removed 2.4 and installed 2.1 and my client wouldn't pick up both my cards. Does anyone use their crossfire bridge while mining? I did a short test and couldn't find a difference in productivity, and it's easier for me since this is my gaming system as well.
If anyone needs dummy plugs here's the guide to make them http://www.overclock.net/folding-home-guides-tutorials/384733-30-second-dummy-plug.html (http://www.overclock.net/folding-home-guides-tutorials/384733-30-second-dummy-plug.html).

Try this, set your mem clock to 300 and on the bat file remove fastloop and add aggression=13. With sdk 2.4 and 980/300 i´m getting 415Mhash/s.

When I tested memory clocks 180MHz-185MHz had the highest increase in speed for me. I do need to adjust core clocks so I'll likely end up adjusting memory clocks as well.
The problem is I can't get aggression=13 to run without crashing yet, even with my relatively high vcore. As soon as finals are over I'm going to try and optimize this as much as possible, and that's why I'm looking for some info from the experienced people around here.

Have you tried SDK 2.1 at all? Nice speeds their, beating me by ~15 at the same core clock.

If I increase or decrease mem clock performance decrease, I don´t remember trying 185 will try. The one time I tried to install sdk 2.1 opencl didn´t work.

Yeah, I believe your ideal mem clock depends on what your core clock is at.

And I had the same issue with sdk 2.1. I need to look into that more (can't wait for finals to be done).

Just for a comparison I run 2 5870s at stock voltage 990 core, 800 mem.  Its a gigabyte and if i run it below an 800 mem clock it tends to wig out, or crash.   Currently im running  Slackware 13.37 stream 2.1 sdk, 11.4 catalyst and am averaging about 420 mhash/gpu.   none of the 5870s are connected to a monitor currently I use onboard gpu for my graphics, and it seems to work much better without tieing down one of the cards to the gui. 

That's pretty darn good. Perhaps I rushed my overclock too much (that's what school does to you : /), seeing as how you got their on stock voltage. And using onboard graphics is a great idea, I wish my mobo had that as well or I would have already tried it!

Yes switching the onboard graphics has really helped my mhash performance.   Ive also speculated that instead of onboard perhaps a small pci hd3000 series or something would also suffice since they are both ati you shouldnt have much trouble with the drivers.   The only thing with windows i believe you will have to have dummy plugs for the adpters or the catalyst won't let you use them or configure them and im not sure what the performance would be with a dummy card as well.

I'm running 2x5870 @stock voltage, 1Ghz core/ 300Mhz mem. I'm getting about 440Mh/s per card. Catalyst 11.3/Stream SDK 2.1/Ubuntu 10.10.

I'm running my 5870 @ 950mhz core and 180mhz memory with stock voltages. I'm getting about 400 Mhash/s. I would push my OC higher but it has been really warm here the last few days and it has been running a little hotter than I like.

I'm running 4 x 990/610, stock voltage, fans 100%, Catalyst 11.5 SDK 2.4, poclbm -v -w128 and pushing 410-420MH/s
Temps around 60C on all cards (all are in separate PC's)

Whenever I try to go to 1000 or above the cards instantly lock up.

I'll be trialing linux tomorrow with SDK 2.1

I use my 5870 in my gaming rig so the following configuration only runs overnight (got a couple of batch files I run with different settings) but:

950Mhz Core
300Mhz Memory
210W Power Use (188 + OC)
Peaks at 80C on XFX stock cooler, drops to 65-70 if I leave my window open (British summer time at its best  :-\)

420Mhash/sec (Well, it averaged 419.83 last night so close enough)

Using phoenix miner 1.48 on Windows 7 x64 with the following settings:

-k phatk VECTORS BFI_INT AGGRESSION=14 WORKSIZE=256

Using CCC 11.5 and SDK 2.4.

I can get it to spike to almost 450 using a high clock speed up to around 990 (1000 causes instant crash and I don't feel like toying with the BIOS/Voltage) but these clock speeds aren't amazingly stable and I don't fancy a crash in the middle of the night while I'm asleep.

Forgive me for asking the noob questions (feel free to flame / point me in the right direction)

But.... I have an i7 w 6GB ram Win7 64bit etc, and an MSI 5870 Lightning, decent card, but on stock gives me only 260MHs (1.12V, 900Clock and 1200Mem).... Starts off with 380, but then winds down over a couple of mins to 260, fan at 100% all the time. Card is sitting at 96 degrees (3 days non stop so far), but is actually cold to the touch (took side fans off to check its really that hot).

Anyway, I tried to follow the above with flags and edited my config for MSI (both that and CAT are latest), and would only let me drop the mem clock down to 600. As soon as i apply that, thinking its going to run ok, the temp goes from 96 to over 100, and at that point, the pc locks up (when mining, is stable in the os for that, temp goes up about 10 degrees but no issues).
Feeling a bit silly with only 260 :( and def not sure what im doing wrong....

The card shouldn't be running that hot - I would guess the reason it's slowing down after a few minutes is that thermal protection is cutting in. I wouldn't recommend running a 5870 at more than 90C for extended periods (and obviously lower is better).

The fact that you're getting those temperatures at stock settings suggests a problem with your setup. Probably the most likely thing is no airflow. Work out where the air is going - make sure you have case fans that are working properly and are configured to take hot air away from the graphics card. Also check that the graphics card fans are working properly and that the heatsink is properly seated on the GPU.

If all else fails install the latest MSI afterburner (or equivalent) - if you decrease the stock voltage by about 10% (exact amount is trial and error, test for stability) and the memory clock down to about 600MHz the card should run a little cooler without reducing hashing performance. I suspect you have a hardware issue though and that any amount of tweaking won't make a vast difference, so look into that first.

Cool thanks for the info I did not think I could push those cards any more than what was out of the box.

I do NOT have a 5870.

However, my 5850 is pulling 350MHash/s with -v -w128, 965MHz GPU, 1000MHz Mem, catalyst 11.5, default voltage

Yeah, am starting to think is hardware. My rig is in a large case with 2 (120) fans drawing air in from the front, one from the side directly onto the vid card, and then two drawing out the top(140's) and one out the back(120), so airflow is not a problem.
Have a large Zalman cooler on the CPU, and that sits and 40-50 on full load, have fantastic cable management (there is a huge amount of space around the vid card for nice airflow) and the fans on the card are defntly working. Am thinking the temp sensor on the card is wonky, or something isnt right. Its getting full voltage from the psu (the card has LEDs that change depending on how much power is going in, and these are always on full).

50Million: I'd start with checking if the cooler is properly mounted on the card. If the heatsink is cold to touch, it would be a likely indicator that it doesn't connect properly to the components.

Edit, more info: The low hashrate you're seeing would probably be due to the GPUs thermal throttling kicking in. When you try to change the memory setting it probably overrides the throttle and tries to run the core at default clock rate, which causes the card to overheat and crash/shut down.

I had a GTX 260 with the earlier version of MSI's twin cooler. It's a card with similar heat output (overclocked from 580 to 655 as well), and it kept the GPU well below reference temperatures with the fans running at about 45%. So, I'm at least fairly confident that you're having a cooling problem.

Anyone else have a Gigabyte GV-R587UD-1GD?  I've only managed to get keep it stable at 950mhz clock, and it appears that other 5870's have been able to go considerably higher.  I think it could go higher if I could increase the voltage a bit but I haven't found a software yet that will do it and I don't want to tinker with the BIOS unless someone else has had success.  Just wondering if anyone has gone higher on that card and what suggestions/settings they might have.

I have an xfx 5870 that wont go stable above 940 in linux, I have flashed the bios with RBE but the voltage control table is missing all of its information and I cannot figure out how to increase it to make it stable.
I have a sapphire version also that goes right up to 985 stable without having to modify the bios.

Very strange  ???

Not really, that's just how hardware works. Each chip will be stable at a different speed/voltage as it comes off of the line. The stock clocks are set such that 100% of the chips that are actually used in production cards will be stable in almost all cases at those speeds. Some have more headroom than others.

The hardcore overclockers (the type who compete in this stuff) will buy numerous chips/cards and test each one individually to find the fastest unit. Variations can be huge.

I have 3x Gigabyte 5870 OC models (870MHz default core) that look like yours, and they are stable at 975 except one of them needs a little lower (5-10MHz) to be stable. Though I guess it's possible that these OC models have increased voltage from defaults, 1.163V according to GPU-Z.

I believe you can overvolt these with gigabyte software, which you can probably find from the driver CD. Haven't tried it myself and probably won't, as I doubt it would be worth it. Most 5870s really don't go much higher than that, 1GHz+ is very rare afaik and most will be 950-1000MHz at manageable voltage.

Mine do 433MH/s in Ubuntu, 975/300 clocks, phoenix w/ poclbm kernel, aggression 12 worksize 256 fastloop=false.
427 in Windows at same settings, except phatk kernel as it seems to be faster in Windows.

Thanks for the info.  The stock voltage on mine is also 1.163 but it is stable at 950 and unstable at 955.  I wasn't sure if the gigabyte software would adjust voltages but based on your results it isn't worth my trouble.  I run mine aggression 9, worksize 128, and phatk asince I do use the card for video output and need it to be somewhat responsive and I get about 408MH/s.   

I have 2x Sapphire Vapor-X 5870 OC running at stock voltage (1.16 V if I remember correctly), 935 MHz core and 319 MHz mem clocks. No CrossFireX bridges. Windows 7 32-bit, Catalyst 11.5 w/ bundled SDK 2.4. Running Phoenix 1.48 + phatk. Options are: VECTORS BFI_INT WORKSIZE=256 FASTLOOP=false AGGRESSION=13. Getting 413 Mhash/s from each card. The rig is located in a conditioned room alongside other IT equipment. With both fans at 100% and with case's side covers removed core temperatures are 45C and 75C (the second card sits too close to the first because of bad PCI-E slots separation).

I edited the file in question,but still can't tweak the voltage.

I'm getting 435 with mine with core at 990 and mem at 185. Stock voltage and phoenix with phatk. Sitting around 70c with fan at 85%.

getting a nice 440-460 Hash with my 5870, clocked to 1Ghz and 185 mem clock using AMD clock tool. Using msi afterbruner to run gpu fans at 100% after 50c, currently stable at 74c, been running for 5 days now, averaging 1BTC-1.1BTC per day. Whenever i try and take my mem clock to 200-250 or below 180, as well as taking gpu to over 1Ghz i get heavy artifacting, I end up having to go into safe mode, use driver sweeper then reinstall CCC 11.5. Also running SDK 2.4

My flags are:

phoenix -u http://username_1:pass@btcguild.com:8332/ -k phatk VECTORS BFI_INT FASTLOOP=false AGGRESSION=13 DEVICE=0 WORKSIZE=128

BTW

Ive ran deepbit, slush and btcguild each for at least 24 hours, in my honest opinion BTCguild is bringing some nice speeds, although i do get periods where theres no work, but this last for a max 4 seconds, hardly any refused shares and take into account the 0% fee!

Ive also ran Phoenix and POCLBM, again, my best speeds were gained using phoenix and the phatik flag.

Now planning to buy either another 5870, or a 5870x2 (drooling at the 850 hash rate!)

Good luck finding them. Every site I have checked is sold out and there are no stores like Fry's anywhere near where I live.

ive found someone who has a faulty 5870x2, judging from what he diagnosed it with i reckon 10 mins in the oven should bring it bk to life

Update:
Removed the card, cleaned the TIM off the chip (looked like someone was trying to fill a lake with the stuff) and put some arctic s 5 on there. Re mounted the cooler, tightened up the back holder plate thing, and cranked it up.
Started off pulling 380M at default clock speeds for the card (900 and 1200), and was fine at this for about 3 mins, but the temp was slowly going up and up... When it hit 90, the card then dropped the clocks (mem and main), as if throttled. But, in saying that, it now pulls 320 instead... so slight improvement, but still not right.

Hi,

I have 3 XFX HD5870 Cards. My max MHash/s is approx. 380. I cannot go over 400 :-(

I'm using poclbm (according to this instruction http://forum.bitcoin.org/index.php?topic=7514.0) on Ubuntu 11.04 64 Bit with SDK2.1.
I overclocked the GPU Core to 900 MHz, and decreased the Mem Speed to 900 as the command "aticonfig --od-setclocks=900,900 --adapter=all" don't let me go under 900 MHz.

How did you set the GPU Mem Speed to 300 MHz. And can somebody explain it to me why this increases the MHash/s rate?

What else can I do to get some kind of 400 MHash/s?

Thanks!

use the amd clock tool, input figures in small incriments. I got 1000 mhz and 185 mem getting 440 on my 5870

Hi The Koolio,

thanks for your answer. Where can I get the amd clock tool? Sounds like a win tool, doesn't it? Where can I got it for Ubuntu?

Another question: Is there also a fan and temperature GUI tool for Ubuntu to monitor ATI Cards?

I'm still intersted in the relationship of low GPU mem speed to higher hash rates  ???

AMD clock tool is for Windows only. Try the AMDOverdriveCtrl tool on Linux.

yeh read the above comment, i can only talk for windows. Have you tried flashing your card?

OK, will check AMDOverdriveCtrl in Linux. Will report later.

Flashin the graphics card? No. Never heard about that. What the advantage? How can I do it?

Again, why does it help to increase hash rate when decreasing the mem speed? What's the dependency?

Thanks

ive extensively tested different techniques

I have two 5870's
1 - Saphire Vapor-x 1 GB
1 - Saphire EyeFinity 6 Version - 2 GB

Your Optimial Clocking...
980/180 (no need to mess with voltage) 75% Fan
poclbm Guiminer actually is faster than phoenix with this card
You will Get 412-420 MH/s

You can overclock it a little more and get about 10 MH/s more out of it but it wont be stable
these cards will run at 980/180 for years as long as there is sufficient airflow/cooling

Hi,

done some tests:

AMDOverdriveCtrl
Nice tool, showing temp and fan and much more. You can use to over- and downclock the ATI devices. I could downclock the Mem speed to 300 successfully. Going further down to 250 and below crashed the screen, using ubuntu 11.04 with ubuntu classic GUI.
But there is no way to overclock the GPU over 900 MHz. How this can be done under linux? Is there any way?

btw: downclocking the Mem speed didn't chnge any MHash/s rate. It's 380 MHash @ 1200 MHZ or 900 MHz or 300 MHz. So why downclocking here? Changing the VCore didn't changy anything. In my case only overclocking of the GPU speeds up the hash rate.

phoenix
using phoenix with phatk kernel instead of poclbm pushes my hashrate near to 392 MHash/s but only with Agrresion=13. Problem, the GUI is nearly not useable afterwards, it's extremely slow!

./phoenix.py -u http://xxxxxx/ -k phatk VECTORS BFI_INT FASTLOOP=false AGGRESSION=13 DEVICE=1 WORKSIZE=128

So, in my opinion to get over 400 MHash/s with a 5870 device you have to overclock the GPU to at least 950-980 MHz. But how can I do this?

Maybe I should switch to Windows, how is stability?

Thanks

I'm getting 413 Mhash/s on both my 5870s clocked at 935 MHz core and 319 MHz memory. The point in downclocking the memory is to conserve power and to reduce the heat output, thus lowering card temperature and displacing the inevitable failure further in time. GDDR5 uses lots of power even when idle and lowering it's clock speed two- or threefold reduces the memory power usage accordingly.

Finding the optimal clock speeds is a tricky optimization task. CMOS logic power consumption is proportional to the clock speed and to the square of the voltage. Hashing still uses the card's memory for some storage and time misalignment between GPU's and memory's clocks can lead to wait cycles when incommensurable frequencies are set.

Hi icaci,

are you running linux or windows? if linux, how did you get the 935 MHz on the GPU?

I'm running 32-bit Windows 7. What you can probably do is to modify your card's BIOS. I've read stories of people flashing their cards' bioses with reference ones from ATI and/or editing existing power states. There are number of tools to do that, for Windows only I presume. Personally I have never done such a thing as my mining rig is a dedicated one and I had access to a genuine Windows 7 license.

ATI HD5870
Catalyst 11.5
SDK 2.4
975MHz core / 333MHz memory
1.250v

Phoenix parameters: -u device=0 VECTORS BFI_INT AGGRESSION=14 WORKSIZE=256 -k phatk

430.xx MH/s, stable
69-70C @ 50% fan speed with case-cover on

Everybody told me to try 300MHz for the memory and that kicked the MHz up quite a bit.  After a little experimenting I found the sweet spot to be 333MHz (using ATI GPU Tool) which increased the hash rate by about 6-8 MH/s over 300MHz memory clock on my system. YMMV.

what kind of motherboard and psu unit are u guys running?

I'm running 2x xfx 5870 and found the sweet spot was 970/386. Getting stable 427mh at 62 degrees. Didn't change my voltage. Sdk 1.4 and ccc 11.5 on win7 64. Only issue is 100% cpu but turns out it's not actually using 100%... I.e. the box can still happily act as a fileserver with no drop in performance. Using phatk with phoenix. Remember that phatk is specifically written for the 5870 so if you have one you should be running it!

 Will

Didn't realize so many people had been responding lately. Anyways I've got my 2 5870's in a good configuration now.

They are at 980 core, 180 memory, 1.187vcore. I keep em around 55% fan speed depending on if i'm in the room or not and the cards are at ~77c and ~82c. My whole system (i7 920, 2 hard drives and 6gb of ram) consumes about 550W at the wall. I'm using phoenix (a few versions older than the newer one) with phatk at aggression 13 and fastloop=false. Each runs just bellow 440mhash/s in phoenix using the latest amd drivers. This is all in windows 7 64bit.

How did you get the 1.250 V setting? Under Ubuntu with AMDOverdriveCtrl I can only get 1.165 V. That's a maximum. Running at 975 MHz Core is pretty much unstable. Do I have to flash the GPU BIOS?

Why do you have the voltage at 1.250v? Is your 5870 unstable with less voltage at 975MHz?

Hi hugolp,

in my case when I go up to 975 Core @ 300 Mem the system freezes few seconds later... I think the GPU gets too less power?
Using Ubuntu 11.04 with SDK2.1.

EIDT: This GPU is the main graphics card onboard, which means it has to support the GNOME GUI as well. Maybe you can run 975/300 with a second GPU responsible for mininig only?

Hi, its weird. Im using Ubuntu 11.04 with SDK2.4 phoenix/phatk. I have 2 Asus 5870 with 1005Mhz core and 335Mhz memory with 1.070V (one needs 1.072V) and they have been running fine for 3 or 4 days now. Today I got an XFX 5870, had to flash it with the Asus limits because it would not allow to go over 900Mhz by default. Now its running with core at 995Mhz and memory at 335Mhz with 1.070V and it has been there for a couple of hours without a problem. I pretend to push it to 1005Mhz slowly.

I understand some differences from different vendors, but needing 1.250v to get 975Mhz seems too big of a difference.

EDIT: One on the Asus was taking care of the screen (with Gnome-Unity) and it was fine. Now the XFX is taking care of it, but I dont think it makes an impact, I mainly use it through ssh and the screen is off all the time. Is there an advantage of using traditional gnome from unity while mining?

With what soft do you measure your voltage?

I have ASUS HD 5870 V2 with 1.212 stock voltage and it does not want to go even to 1GHz core speed(((

And what are the temps?

I live in Ukraine and it is quite hot here now, so my cards with 100% fans do not go higher than 82C according to MSI AB.

I've got 1xASUS 5870 and 3xGigabyte GV-R587UD-1GD with core\mem 990\365 for ASUS and 960\365 for others. Found out that this is the best mem speed for my setup!
Wanted to push voltage higher on Gigabyte cards with Trixxx and AB but got no success. The only way is modifying voltages with RBE but there are a lot of cautions over the forums that any voltage manipulations with non-reference cards result in BSOD.

The wierd thing is that I updated BIOS on Gigabyte cards (had F1, F5 and F7) to F8. RBE shows that stock voltage is to be 1.163 but GPU Shark says that one of the cards is working with 1.125 core voltage. WTF?

Anyone has some experience in voltage manipulation with GV-R587UD-1GD?

Im setting it with AMDOverdriveCtrl.

Hi hugolp,

that's really weired. Same brand but different behaviors... Maybe it has something to do with the relationship between core and mem speed. I tried 950, 980 and 1000 core speed at 300 mem speed. All freezed. Now I'm running really stable at 930 core and 300 mem speed (410 MHash/s phoenix/phatk). Maybe I should take mem speed up a little bit to 333 or 335. Maybe that's the point. I don't think SDK 2.4 makes the difference. And I don't think there is a diffenernbce in Gnome Classic and Unity. I don't like unity, that's all.

I'm setting it with AMDOverdriveCtrl as well, but cannot go over 1.165 V on XFX HD5870 XXX.

Thinking about it I think that at 1005Mhz if I pushed the voltage higher it would run for a while and then crash. You might want to test at 995, 1000 or even 1005 at lower voltages, like 1.070v for me. At 1010Mhz and 1015Mhz it would run for a while but there was no way of making it stable. Also, by lowering the voltage you get better consumption theoretically.

If this does not work its very weird because I could have gotten a couple of mega-asus, but Im almost in the same situation with the XFX.

And what are the temps?

I live in Ukraine and it is quite hot here now, so my cards with 100% fans do not go higher than 82C according to MSI AB.

I've got 1xASUS 5870 and 3xGigabyte GV-R587UD-1GD with core\mem 990\365 for ASUS and 960\365 for others. Found out that this is the best mem speed for my setup!
Wanted to push voltage higher on Gigabyte cards with Trixxx and AB but got no success. The only way is modifying voltages with RBE but there are a lot of cautions over the forums that any voltage manipulations with non-reference cards result in BSOD.

The wierd thing is that I updated BIOS on Gigabyte cards (had F1, F5 and F7) to F8. RBE shows that stock voltage is to be 1.163 but GPU Shark says that one of the cards is working with 1.125 core voltage. WTF?

Anyone has some experience in voltage manipulation with GV-R587UD-1GD?

Quite low, never over 60º. Its getting hot here too but I run it without a case in a room with two windows open and a 20W fan next to the whole thing. Here you go:

Adapter 0 - ATI Radeon HD 5800 Series
                            Core (MHz)    Memory (MHz)
           Current Clocks :    995           335
             Current Peak :    995           335
  Configurable Peak Range : [600-1200]     [335-1400]
                 GPU load :    99%

Adapter 1 - ATI Radeon HD 5800 Series
                            Core (MHz)    Memory (MHz)
           Current Clocks :    1005           335
             Current Peak :    1005           335
  Configurable Peak Range : [600-1200]     [335-1400]
                 GPU load :    99%

Adapter 2 - ATI Radeon HD 5800 Series
                            Core (MHz)    Memory (MHz)
           Current Clocks :    1005           335
             Current Peak :    1005           335
  Configurable Peak Range : [600-1200]     [335-1400]
                 GPU load :    99%

Adapter 0 - ATI Radeon HD 5800 Series
            Sensor 0: Temperature - 55.50 C

Adapter 1 - ATI Radeon HD 5800 Series
            Sensor 0: Temperature - 56.00 C

Adapter 2 - ATI Radeon HD 5800 Series
            Sensor 0: Temperature - 56.50 C

Voltages are (0)1.070, (1)1.072 and (2)1.070.

I will post pictures of the whole thing when I  get the fourth.

EDIT: The fasn are running at 95% (dont like to run them at 100%) and if I turn the big fan off the temperature raises like 10º, never over 70º, although the fan has been always on when it has been hot. Actually, the big fan is on for the rest of the parts of the card that seem to run very hot. Does anyone know how to access the rest of temperature sensors of the 5870 from linux?

Cool in every sense :) :) :)

Thanx!

I'm thinking of installing a fan now ::)

Here is my rig:
http://forum.bitcoin.org/index.php?topic=7216.msg226664#msg226664

I will give it a try in the next days, will come back here withn the results.

WinXP-32
guiminer/poclbm -v -w128 -f 1
SDK 2.1, Catalyst 10.11
Sapphire 5870
73-75 C, 40% fan speed
stock voltage

Core: 900
Mem: 314
Rate: 392 MH/s

I will eventually attempt to overclock it some more, but want to verify stability at this level.

Things that I found are bad:

1. Having Catalyst Control Center installed. If I got a crash, the next time I rebooted, CCC would attempt to set ridiculously low clock speeds, which would immediately crash the computer again. Gone.
2. Attempting to underclock the memory while the miner is running. This caused crashing when I dropped the memory below 500. Now I am down to 300-314 without issue.

Things that are good:

1. Installing SDK 2.1 in place of 2.4 boosted hashrate by up to 10 MH/s.
2. Slightly increasing the fan speed using a custom profile in Afterburner helped reduce the temperature to a more comfortable setting.  :o  ;)
2. Dropping memory clock to about 1/3 of core clock: lowered temperature by another 7-10 C.
3. Increasing memory clock by 14 after setting it to 1/3 of core clock: increased hashrate by 1-2 MH/s.

Things that made no difference:

1. Installing Catalyst 10.11 in place of the latest version. (I verified that the driver version was correct in device manager).

This depends on the software you are using to mine. F.e. poclmb goes better with 2.1 and phatk goes better with 2.4. I get better results with phatk+2.4 than any other combination.

guys i need a mother board for 3 5870s and a psu that supports it.

I have no control over my voltage.  That's what the AMD GPU Tool sets it at automatically any time I specify any kind of OC value to the core.  I thought it was kinda weird, but it works.

I had been searching for this solutions for days. You are awesome! My GPU thanks you with its cooler temps!

Bitclockers.com (http://www.bitclockers.com) Mining pool has a very helpful forum with guides on configuring 4, 5 and 6 series graphics cards.
http://bitclockers.com/forums/index.php?topic=6.0
there is also an overclocking guide to help you get started
http://bitclockers.com/forums/index.php?topic=5.0

No problem! Feel free to donate to my cause if I've been helpful. Let's say, 1 BTC per degree Celsius improvement.  ;D

how did you guys get SDK2.1 to work? the latest ATI driver that that compatible with SDK2.1 is 10.4. and when i installed 10.4 with 2.1, i get the error msg "no openCL found" when using GUIminer  ???

solved it by first installing SDK 2.4 > uninstall SDK 2.4 > install SDK 2.1 :p

XFX
1020 Core
350 Mem
Stock Voltage
63 C
450Mhash

11.6 Drivers