Bitcoin Forum

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?

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.

http://www.digikey.com/Web%20Export/techzone/power/article-2012august-front-end-ac-dc-fig1.jpg

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

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 ?

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

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

1200W is enough but if you want to overclock then go for LEPA G1600

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.

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

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'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

Speaking of such, I've got one that is 2 months old max that needs a new home.  I'll ship it to you (continental US) for BTC equiv of $175.  Going to list it soon in the computer for sale  section...
 
M

EDIT: didn't mean auction

I get 1090-1130w undervolted, definitely go with a 1200-1250w psu

1200w psu can handle 4x7970 or 5x7950

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

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.

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).

That date has come for me too. Been running several 2 PSU rigs for 2 yrs.