What are the steps I can take to save power on mining rig?

[kokojie]

Trying to build my first mining rig, 3 x 6970, 1000 watt PSU, but looks like I underestimated the 6970 power consumption. The rig won't start with 3 card, will only boot with 2. I'm wondering how can I possibly save power to have the 3rd card added.

FYI:
CPU: AMD athlon X4 640 (95W, 3.0Ghz)
MoBo: MSI 890 GD70
HD: 1TB WD SATA3
RAM: 4GB single stick corsair
FANS: 4 case fan

I'm thinking maybe dropping the CPU frequency to somewhere 1.5 Ghz, this would still allow me to run ubuntu 11.04 without problem right?

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[Caladain]

1000w PSU, if it's putting out 1000w, should be more than enough.

Check your mobo manual and see if certain PCI slots have to be populated in a different order if 3 cards are used..

Have you tried each card individually to make sure you don't have a bad card that's preventing boot?

Donate(if it helps :-): 1QDMjbtTvekcYnskmZVoUEGMsecEvzgFHQ

Edit: Also, can you post up the full name/spec of your PSU?

[smoki]

Not all 1000W PSUs are equal... which one exactly did you get?

As for saving power:
 - disable all but one core on the cpu (yes, it will be enough for a dedicated rig)
 - downclock the cpu as low as it will go, then decrease the cpu voltage as low as possible while keeping the cpu stable
 - dowclock the video memory on your cards down to the 150-300MHz range (this can also improve your hashrate)
 - replace the hdd with a usb stick

You should be able to get the cpu down to 10W or less, removing the hdd saves 5-10W (depending on model) and downclocking video memory saves 20-30W per card.

[computerparts]

A 1000w psu should be more than sufficient but we need to know what psu you are using. I do not recommend undervolting any cpu below its specs. Regardless if it seems stable, long term damage still applies. Also please be more specific on what you mean by "rig won't start". Do the fans power up on the cards? Does anything power up at all? We need more info. 

[smoki]

CPUs are speced to undervolt, they do it on their own anyway, when idle. The Athlon X4 640 has an operating voltage range of 0.875V-1.425V. Running it at something like 1V and 1.5GHz will, if anything, probably extend it's lifetime.

[kokojie]

Thanks for the reply, the PSU is a corsair
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139007

When I have 3 x 6970 in the rig, the system will start for 1/2 a second and then dies, nothing would power on (though mobo still show the small power indicator light). If I put 2 x 6970, then system would boot up fine.

A 1000w psu should be more than sufficient but we need to know what psu you are using. I do not recommend undervolting any cpu below its specs. Regardless if it seems stable, long term damage still applies. Also please be more specific on what you mean by "rig won't start". Do the fans power up on the cards? Does anything power up at all? We need more info. 

[gigabytecoin]

Thanks for the reply, the PSU is a corsair
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139007

When I have 3 x 6970 in the rig, the system will start for 1/2 a second and then dies, nothing would power on (though mobo still show the small power indicator light). If I put 2 x 6970, then system would boot up fine.

A 1000w psu should be more than sufficient but we need to know what psu you are using. I do not recommend undervolting any cpu below its specs. Regardless if it seems stable, long term damage still applies. Also please be more specific on what you mean by "rig won't start". Do the fans power up on the cards? Does anything power up at all? We need more info. 

Try lowering the "Boot" clock speeds (cut them in half) using Radeon Bios Editor and re-flash each video card. Should use about half the power on boot up.