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Author Topic: 1000w enough for four 7900 cards?  (Read 1338 times)
ryantc
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June 01, 2013, 09:41:54 AM
 #1

I need to rearrange some of my cards
Currently I am running 3*7950 + 1*7850 on a 1000w platinum psu
and I am thinking to swap out the 7850 and add a 7970 instead

if I undervolt all my cards (they are all working @ 1.05v happily), and put mem clock to insanely low
on a 775 E7200 platform with 1 RAM and 1 SSD

am I pushing the PSU too hard?

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lucazane
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June 01, 2013, 09:53:54 AM
 #2

The PSU should be ok.

But I always try to have my mining rig at less than 80% percent of PSU load.

if you look at this chart, you can see that the typical PSU efficiency go down after 50% of load.



With your configuration, you will be between 900 and 1000 w. I would go for at least a 1200w PSU.

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June 01, 2013, 10:28:08 AM
 #3

i'm still trying to figuring out,

wouldn^t it be cheaper to use

2x 600w PSU or 
1x 600 + 1x 750w  or
2x 800w ?

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pajak666
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June 01, 2013, 12:46:57 PM
 #4

definetly go 1200w for 4 gpu's
1000w is not enough
3x 7950 + mobo + cpu + ram = ~830-960 W, so 1200 should be enough for 4 x 7900
ryantc
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June 01, 2013, 01:45:03 PM
 #5

thanks for all your replies

en......have another thought, can I add another 500w e.g Corsair cx500 on top of the 1000w to run the 4 7900 rig?
I mean in terms of wattage this time it should be enough, but is it safe enough to do it this way?

I might have some misinformation that cards, wires, PSU itself get burned because of this kind of setup, so I am a little hesitate



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June 01, 2013, 03:50:56 PM
 #6

1200W is enough but if you want to overclock then go for LEPA G1600
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June 01, 2013, 10:09:50 PM
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To date I have yet to hear of one person happy with their dual PSU setup, almost always leads to problems. I am intrigued by the product http://www.newegg.com/Product/Product.aspx?Item=N82E16817206001 however I do not know if it is a good value, but that's probably one of the only ways I'd recommend dual PSU.

You are probably running your PSU close to its limit, so maybe underclock/undervolt a bit and hope for the best.
crashoveride54902
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June 01, 2013, 11:09:51 PM
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Ok that date has come...I'm running 3x7970's oc'd off my seasonic 860w n offbrand 600w psu without a problem Smiley

To date I have yet to hear of one person happy with their dual PSU setup, almost always leads to problems. I am intrigued by the product http://www.newegg.com/Product/Product.aspx?Item=N82E16817206001 however I do not know if it is a good value, but that's probably one of the only ways I'd recommend dual PSU.

You are probably running your PSU close to its limit, so maybe underclock/undervolt a bit and hope for the best.

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June 01, 2013, 11:27:46 PM
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So I just built a 4 x 7950 setup with an AMD Sempron 145 processor and 3 GB of RAM. It pulls down just over 1150 Watts with the GPU's overclocked (and GPU memory underclocked) and with a physical HDD.

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June 01, 2013, 11:30:45 PM
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Ok that date has come...I'm running 3x7970's oc'd off my seasonic 860w n offbrand 600w psu without a problem Smiley

To date I have yet to hear of one person happy with their dual PSU setup, almost always leads to problems. I am intrigued by the product http://www.newegg.com/Product/Product.aspx?Item=N82E16817206001 however I do not know if it is a good value, but that's probably one of the only ways I'd recommend dual PSU.

You are probably running your PSU close to its limit, so maybe underclock/undervolt a bit and hope for the best.

I've done it (two, even triple PSUs) as well.  I've since switched to Rosewill lightning 1300 PSUs:  

http://www.newegg.com/Product/Product.aspx?Item=N82E16817182063&Tpk=rosewill%20lightning%201300&IsVirtualParent=1

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June 02, 2013, 04:33:04 AM
 #11

So I just built a 4 x 7950 setup with an AMD Sempron 145 processor and 3 GB of RAM. It pulls down just over 1150 Watts with the GPU's overclocked (and GPU memory underclocked) and with a physical HDD.

I get 1090-1130w undervolted, definitely go with a 1200-1250w psu
ronaldinho_07
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June 02, 2013, 09:28:27 AM
 #12

1200w psu can handle 4x7970 or 5x7950
crashoveride54902
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June 03, 2013, 02:46:46 AM
 #13

i'm now also running 1 7970, 1 5970, n 1 5850 off a 860w n 300w psu Cheesy gotta use what i got...still have 1 card idle..only a 5770 so not a big loss...

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June 03, 2013, 04:21:32 AM
 #14

I've got 1x 7970 and 3x 7950 all heavily oc'ed with light under volting running on an 1100watt psu with absolutely no problems what so ever.

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June 03, 2013, 06:20:12 AM
 #15

Depends on your GPU (overclocking) settings. I run my 4 x Sapphire 7950 rig undervolted:
VDDC: 0.993V
GPU: 930 MHz
RAM: 1250 MHz
at 845 W (~200 W/GPU). Hash rate (per GPU) is 565 kH/s (Litecoin) or 560 MH/s (Bitcoin).

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June 03, 2013, 02:32:41 PM
 #16

Ok that date has come...I'm running 3x7970's oc'd off my seasonic 860w n offbrand 600w psu without a problem Smiley

To date I have yet to hear of one person happy with their dual PSU setup, almost always leads to problems. I am intrigued by the product http://www.newegg.com/Product/Product.aspx?Item=N82E16817206001 however I do not know if it is a good value, but that's probably one of the only ways I'd recommend dual PSU.

You are probably running your PSU close to its limit, so maybe underclock/undervolt a bit and hope for the best.
That date has come for me too. Been running several 2 PSU rigs for 2 yrs.

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