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Author Topic: 4 x 7970 psu?  (Read 6232 times)
ge0rgieee
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May 17, 2012, 04:37:54 AM
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Do you think its possible 1 PSU can run 4-5 7970's in 1 system?
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nckrazze
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May 17, 2012, 04:39:08 AM
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1500w+ for sure.
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May 17, 2012, 04:39:19 AM
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Yes. Tongue

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ge0rgieee
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May 17, 2012, 04:50:26 AM
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what about 5 x 7970's with this: http://www.newegg.com/Product/Product.aspx?Item=N82E16817151109
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May 17, 2012, 05:03:02 AM
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This is what you need for 5. Average power consumption for 3 7970's is around 900w so 1500w for 5 including the mobo and cpu. That's if the power supply actually supplies a full 1500w.
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May 17, 2012, 07:09:14 AM
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Pssh, cmon. Undervolt that shit. You shouldnt need more than a 1KW PSU for 5 7970's, if that. My guess, properly undervolted/underclocked memory/max core @ 0.95v, it would only draw 750w at the wall.

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May 17, 2012, 07:10:44 AM
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I am running 5x 7970's using a single Sparkle Power 1200W 80+ (rated for 900W 12V @ 5 rails)

The total system power draw is 865W at the wall running the cards @ 950Mhz GPU / 900Mhz Mem @ 1.02V, 565MH/s per card.
The system consists of a 790FX-GD70, AthlonII X2 215, 4GB DDR3 and an SSD.

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May 17, 2012, 07:59:49 AM
 #8

To get the most I could (power out of 15A home circuits that is...), I used two circuits (15A each) to split 3 rigs onto.....that looks like this:

(1 full machine & 'in-window' twin cooling fan per circuit, 3rd rig split over 2 circuits to keep from blowing breaker)
Circuit A also has a Dell 24port 10/100 switch (almost forgot about that...lol

All cards running @ 950Mhz GPU / 900Mhz Mem @ 1.02V, 565MH/s per card....(using CGMiner 2.4.1 defaults, Win7 x64)




Both of the remaining 4-card rigs will also get their 5th 7970's installed as soon as the cards arrive.

Hope this helps some people, or gives a few ideas for those wondering....

For those wondering about specific setup...(not including the obvious single power supply 5-card/1200W PSU Rig)...

On the 2x PSU rigs, I use the 850's to power the Motherboard/CPU/HDD + 2 Video Card's External 8pin/6pin connectors (and of course all PCIe Slot Power by association).
The Secondary 650's get used for external Video Card power to the 6pin/8pin connectors to the 3rd, 4th and 5th cards (and perhaps additional cooling fans if required in the future).

bitlane
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May 17, 2012, 08:13:19 AM
 #9

i have 3x 7970s that pull 680w at the wall and are on a 850 watt psu.

That seems a bit high...

What is your MH/s per card ?...and are you overclocking/undervolting etc ?
Share some specs/settings if you don't mind.

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May 17, 2012, 10:30:02 AM
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@bitlane, choosing a x58 Mainboard may be not he best decision. It's Powerconsumption is way to high, CPU also.
But i see also you got a AMD Sys.

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May 17, 2012, 10:58:22 AM
 #11

Couple of questions :

-does the underclock memory trick work with 7970s in Linux without needing BIOS flashing ?

-can 4*7970s at full overclock be used with a PSU of 1200W without power problems ( cards overclocked high ) ?

Thanks !

And ... where are my 7990s Huh Looks like AMD has given up Cheesy
bitlane
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May 17, 2012, 11:02:06 AM
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@bitlane, choosing a x58 Mainboard may be not he best decision. It's Powerconsumption is way to high, CPU also.
But i see also you got a AMD Sys.

AMD licks balls with being limited to x16-x16 risers only in most x16 slots.

The X58 rigs allow me to run any width cable I want in any slot as long as it fits (obviously I can'y run an x16 cable in an x1 slot Wink  )

I just hate messing around with shorting pins etc. Also, my Xeons are 80W CPUs so it's not that bad.

bitlane
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May 17, 2012, 11:05:05 AM
 #13

Couple of questions :

-does the underclock memory trick work with 7970s in Linux without needing BIOS flashing ?

-can 4*7970s at full overclock be used with a PSU of 1200W without power problems ( cards overclocked high ) ?

In Windows:
Using CGMiner/ADL, memory spread is 150Mhz MAX.
Using 3rd party tools (AB, Trixx etc) can turn mem down lower.

In Linux:
No clue.

4x 7970 on 1200W, overclocked ?
Yes, I was running 1150mhz (650MH/s @ 1100Mhz...so higher obviously) on stock voltage (4 cards) and drawing 1000W at the wall
(using a Sparkle Power 1200W 80+ PSU rated for 900W max combined on 5x 12V rails).


And ... where are my 7990s Huh Looks like AMD has given up Cheesy

June/July after some Equipment Show/Conference, also held back due to cooling problems and Nvidia Dual-GPU release.

bitlane
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May 17, 2012, 11:09:00 AM
 #14

i have 3x 7970s that pull 680w at the wall and are on a 850 watt psu.

That seems a bit high...

What is your MH/s per card ?...and are you overclocking/undervolting etc ?
Share some specs/settings if you don't mind.

undervolt to 1.05 overclock to 1050 mem at 900  get about 600mhs per card

Have you found some to be a bit flaky with mem under 850Mhz ?

I am running my mem @ 900Mhz because I was crashing CGMiner at times (regardless of voltage increases). I've now been stable for nearly 48hrs with mem @ 900.
(950Mhz GPU, 900Mhz Mem, V-1.02, 565 MH/s each)

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May 17, 2012, 05:43:41 PM
 #15

I have 5 on enermax platimax 1500W, running them at 1100MHz@1100mV, didnt measure the draw with that configuration and settings but i assume its about 1300-1400W or so (free power so fuck it Smiley)
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May 17, 2012, 07:26:16 PM
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OP Please keep in mind that power draw at the wall is not the power the PSU is giving to the cards. For example if I were to ask my PSU for 1000W and it is 87% efficient (80 PLUS Gold 100% efficiency), then the actual draw from the wall would be 1000/0..87 = ~1150W.

That being said, you might also might want to think about how you're powering all this equipment. Most house circuits in the US are 15A circuits which means you have a really good chance to trip your breaker if you power anything else on that circuit.


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May 17, 2012, 07:54:35 PM
 #17


4x7970 overclocked to 1200/1050 will not pull more than 1250W
5x7970 overclocked to 1200/1050 will not pull more than 1500W

I'm running 3x7970s @ 925/340/0.88, the whole system pulls about 480W from the wall,; ~1660 Mh/s

So it depends how you are going to run them.  If you extremely underclock/undervolt them, you can run all 5 with a 850W PSU,
but if you want to run them full throttle, get 1500W Platinum rated PSU.
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May 17, 2012, 08:01:46 PM
 #18

June/July after some Equipment Show/Conference, also held back due to cooling problems and Nvidia Dual-GPU release.

June 6th, Computex 2012.

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bulanula
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May 17, 2012, 09:04:45 PM
 #19

What about running 4*7970s on 1250 MHz and lowest memory BIOS flashed Huh On AX1200 or SS 1250W models ?
bitlane
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May 17, 2012, 09:51:02 PM
 #20

What about running 4*7970s on 1250 MHz and lowest memory BIOS flashed Huh On AX1200 or SS 1250W models ?

At those speeds, I wouldn't want to deal with the heat and unnecessary power requirements to reach 1250Mhz.

As I said (and can be seen on the BTC Wiki under Hardware Comparison) 1100Mhz gets you 650 MH/s per card. If I recall, 1150 got me roughly 675-680 MH/s.
Unfortunately at that point, heat started to become a concern for me, as I like to run my cards cool and use a 69c target temp and make sure my fans run under 50% 24/7 to achieve it.

Here is a screenshot of my 3x 7970 rigs. As you can see, I am loosing performance but notice my temps (it's also warm today) and I explained my power draw earlier in the thread....this setup runs very efficiently for what it is. (voltage doesn't report correctly through CGMiner API, all voltages should read 1.02V).
With more power available to me, I could easily clock these 3 rigs up and add 100+ MH/s to each card (so, 1.4GH/s total)....but again, at the price of power that I don't have....and heat that I don't want to deal with.

This is a custom web monitor using the CGMiner API.



I am currently running 14 (soon to be 15, last card should be here in a day or so, was on backorder) of these:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814125408
Gigabyte 7970 Reference Models.

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