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Author Topic: Undervolting a 5870 and a 5770 to achieve better MH/J performance  (Read 14368 times)
runeks
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January 16, 2012, 02:33:12 PM
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Hello all

I just recently found out how dramatic an increase in efficiency undervolting can achieve. In my mining rig I'd like to optimize this, and preferably get it to consume around 250W in total. Right now it's consuming around 265W. I'm running with the following voltage/clock settings currently:

5870: 750 MHz / 1.000V / 97W / 343 MH/s / 3.54 MH/J
5770: 750 MHz / 1.010V / 63W / 168 MH/s / 2.67 MH/J

As you can the 5870 is significantly more efficient than the 5770. Then again it's also running at 1V vs. the 5770's 1.01V. But I simply can't get the 5770 to run properly at 1V at 750 MHz. At this voltage it keeps stalling in cgminer ("declared SICK") unless I run it at 700 MHz.

What are people's experiences with 5870's and 5770's and stable voltage/clock combinations of these?

By the way, the 5870 is an HD-587X-ZNFV V1.3 5870, and the 5770 is this Sapphire card, though I'm not sure if it has 512 or 1024MB RAM.
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P4man
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January 16, 2012, 03:02:18 PM
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2 of my 3 5870s do 900 MHz @ 1.05V 
Both my 5850s will do 850 MHz @ 1V

runeks
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January 16, 2012, 03:10:16 PM
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^Cool. Good to know. I'm running at a lower voltage though. It seems even miniscule drops in voltage decrease power usage dramatically:

I just tried setting the 5770 voltage to 1V and downclocking it to 700 MHz. This seems stable. So these become the new figures:

5870: 750 MHz / 1.000V / 97W / 343 MH/s / 3.54 MH/J
5770: 700 MHz / 1.000V / 39W / 158 MH/s / 4.05 MH/J

What a dramatic increase in efficiency from a mere 0.01V drop!

Before reducing voltages, my mining rig would consume about 365W while producing 660 MH/s. Fiddling with the voltages, it now uses 240W while producing 500 MH/s. So that was 1.81 MH/J before, and 2.08 MH/J now. About a 15% increase in efficiency.

I'd love to get a Kill-a-watt device that supports retrieving wattage programatically in Linux, via an USB connection or something. That way I'd be able to make a script that can automatically change the clocks to achieve the best efficiency. It'd be interesting to see what the most efficient clock/voltage combination would be.
DeathAndTaxes
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Gerald Davis


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January 16, 2012, 03:16:10 PM
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Can you try the 5870 @ 0.95V or 0.90V you likely will need to drop the clock some.
P4man
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January 16, 2012, 03:22:35 PM
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IM curious how you measure the power consumption of the cards alone.. ? Are you taking motherboard in to account?

runeks
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January 16, 2012, 03:40:42 PM
 #6

Just tried upping the 5870 clock to 800 MHz. Here are the results:

5870: 800 MHz / 1.000V / 102W / 370 MH/s / 3.63 MH/J
5770: 700 MHz / 1.000V / 39W / 158 MH/s / 4.05 MH/J

So it definitely seems like the voltage is the most important factor in determining the power usage.

Can you try the 5870 @ 0.95V or 0.90V you likely will need to drop the clock some.
I'm trying out the 5870 at 600 MHz at 0.900V now. Will wait for the temps to stabilize and to see whether it's stable.

IM curious how you measure the power consumption of the cards alone.. ? Are you taking motherboard in to account?
I'm simply measuring the wattage at the wall with either or both of the cards turned off in cgminer, and subtracting the wattages. So idle card power is not included in the card power consumption figures.
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Gerald Davis


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January 16, 2012, 03:47:01 PM
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So it definitely seems like the voltage is the most important factor in determining the power usage.

Yeah electrical theory tells us power changes at the square of voltage change.
So 90% of voltage = (0.9^2) = 81% of the power.

Theoretically if you could get a card to run on 50% of the voltage it would use about 25% of the power. Smiley

Power consumption is linear with clock rate.  So 10% reduction in clockrate should be ~10% change in power.

This is why overVOLTING is generally not worth it.  Lets say you overvolt 10% and get 15% higher clock rate.
Your power consumption will increase (1.1^2)*1.15 = 1.395  roughly 40% power increase for 15% higher performance.



I'm simply measuring the wattage at the wall with either or both of the cards turned off in cgminer, and subtracting the wattages. So idle card power is not included in the card power consumption figures.

If you want to be conservative the idle wattage of 5770 is <16W and the 5870 is <28W so subtracting that from rest of idle system would give you the "non" GPU idle load.
runeks
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January 16, 2012, 03:58:38 PM
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^ Interesting DAT. Thanks for the electrical theory lesson Smiley.

The 5870 seems to be stable at 0.90V@600MHz. Here are the figures:

5870: 600 MHz / 0.900V / 61W / 273 MH/s / 4.48 MH/J
5770: 700 MHz / 1.000V / 39W / 158 MH/s / 4.05 MH/J

I'm running the 5870 at 650 MHz now to see if this is stable as well at 0.90V.

Would be interesting to see how high the efficiency can get.

Hmm. I just found out that it seems the leftmost hash rate next to the GPUs in cgminer might be an average-since-start. My previous figures might not be accurate then.

EDIT: The above hash rates are fine.
runeks
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January 16, 2012, 04:05:15 PM
 #9

At 650 MHz the 5870 is about as efficient as at 600 MHz:

5870: 650 MHz / 0.900V / 66W / 295 MH/s / 4.50 MH/J
5770: 700 MHz / 1.000V / 39W / 158 MH/s / 4.05 MH/J

(Hash rate is now measured by a restarted cgminer)
conspirosphere.tk
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January 16, 2012, 04:14:45 PM
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How do you undervolt the cards? Trixx and Afterburner do not work for me (with the first the voltage is locked, and the second is not even able to read current voltage).

P4man
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January 16, 2012, 04:16:11 PM
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I just use cgminer (on linux).

DeathAndTaxes
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Gerald Davis


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January 16, 2012, 04:25:37 PM
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How do you undervolt the cards? Trixx and Afterburner do not work for me (with the first the voltage is locked, and the second is not even able to read current voltage).

You can try cgminer but not all cards have adjustable VRM.  Some cards (especially the cheaper ones) use a non-adjustable VRM to save money.
runeks
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January 16, 2012, 04:29:14 PM
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Does anyone know why my 5870 is stable at 800 MHz at 1V, while my 5770 is only stable at 700 MHz when running at 1V core voltage?
Is it just simple variance in the chips, and it might as well have been the opposite?

How do you undervolt the cards? Trixx and Afterburner do not work for me (with the first the voltage is locked, and the second is not even able to read current voltage).
Using AMDOverdriveCtrl on Linux.
P4man
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January 16, 2012, 04:35:24 PM
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Manufacturing variance could easily explain that, but 5870 and 5770 also use completely different dies ("designs") and probably more optimized for yields than clocks.

runeks
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January 16, 2012, 04:45:44 PM
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How many different GPUs does AMD really make? I thought most of them were the same chip but they just disabled some of the stuff in the cheaper ones to make more money.
P4man
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January 16, 2012, 04:49:59 PM
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How many different GPUs does AMD really make? I thought most of them were the same chip but they just disabled some of the stuff in the cheaper ones to make more money.

5970, 5870, 5850 and 5830 all use the same, relatively large "cypress" die (5970 uses 2 obviously).
57x0 (5750 and 5770 mainly) is a different, considerably smaller die called juniper. Below that you have few other derivatives still, if you want details:
http://en.wikipedia.org/wiki/Evergreen_%28GPU_family%29

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January 16, 2012, 05:36:11 PM
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IM curious how you measure the power consumption of the cards alone.. ? Are you taking motherboard in to account?

From the 7970 thread, you take the difference between system mining wattage and the system idle wattage to get the card wattage.  It's not really exact, but it's at least consistent between different system configs.

Single 7970:
System Idle: 270 watts
System Mining: 388 watts
Mining: 925/150mhz,  865mv, 118 watts
550 MH/s (4.66 MH/watt)

Single 5970:
System Idle: 138 watts
System Mining: 268 watts
Card Mining: 680/166mhz, 950mv, 130 watts
622 MH/s (4.78 MH/watt)

System Mining: 250 watts
Card Mining: 605/166mhz, 950mv, 112 watts
550 MH/s (4.91 MH/watt)

System Mining: 235 watts
Card Mining: 605/166mhz, 900mv, 97 watts
550 MH/s (5.67 MH/watt)

Mousepotato
runeks
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January 16, 2012, 06:08:18 PM
 #18

Can anyone tell me how to get AMDOverdriveCtrl to set clocks and voltages on startup in Linux?
I've tried adding a script to be started in /etc/rc.local which looks like this:

Code:
#!/bin/bash
sleep 30
cd /home/user/
AMDOverdriveCtrl -b -i 3 .AMDOverdriveCtrl/5770.ovdr >> logs/overdrive.log
AMDOverdriveCtrl -b -i 0 .AMDOverdriveCtrl/5870.ovdr >> logs/overdrive.log

But when I start up my mining rig and run aticonfig to see the clocks, they're the default ones, and cgminer reports that the GPUs are unstable.
Could it be that AMDOverdriveCtrl successfully sets the voltages, but then the clocks, for some reason are not set? the log file logs/overdrive.log shows that the script indeed has been run, but for some reason it either doesn't persist or some other program changes the clocks.

When I log in and run the above script manually, it sets the clocks and voltages fine, and aticonfig reports the clocks that I specified in my .ovdr files.

EDIT: Solved
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January 18, 2012, 02:08:22 PM
 #19

Looks like the old 5xxx series still beats the new cards in $/mhash and mhash/watt.  Maybe the 7970 can be undervolted further.
DeathAndTaxes
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Gerald Davis


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January 18, 2012, 02:16:30 PM
 #20

System Mining: 235 watts
Card Mining: 605/166mhz, 900mv, 97 watts
550 MH/s (5.67 MH/watt)

Thats pretty damn impressive.  I mean BFL yet to ship FPGA only get 10MH/W.

I may undervolt my rigs this summer.  Keeping the garage cool with cards puking out 4KW of heat during August is tough.
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