Trouble getting 3 cards working

[neflihim]

Hey all,

I'm trying to get my rig up and running at full force and can't seem to get the 3 card running/detected.

Here is my Set up

2xMSI 7970 Twin Frozr
1xMSI R9 280 Twin Frozr
Asus P6T Mobo
i7 900 series Proc
12 Gig (6x2gb) Corsair RAM
Corsair HD1050 PSU

Cards are installed catalyst 13.x

When I have 2 cards, in any combo ie: 1x7970 1x280 or both 7970 I can get the system to run stable.  As soon as I add the 3rd card the system falls to its knees and crashes eventually.  This is before I'm even hashing at all.  It loads extremely slow booting to windows and once booted is basically unusable.  At first I thought I was having a problem with my riser cables but I took those out of the equation and installed the cads directly onto the board and I got the same issues.  Any ideas would be appreciated. 

Thanks

[1714251650]

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[1714251650]

1714251650

[1714251650]

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[1714251650]

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[wpgdeez]

You probably need a slightly larger PSU.

[neflihim]

1050 Gold rated Corsair isn't enough?  Tomshardware rates these max load somewhere in the realm of 250W a piece.  Should be plenty.  I guess I can try using dual PSU's and see if that works. 

[wpgdeez]

If you are oc'ing the cards you could easily be pulling 300 watt per card, plus your cpu, fans, drives etc. Worth a shot splitting 1 card off to another PSU to test.

[pontiacg5]

It crashes before mining is ever started? Are you sure?

That's not a sign of a weak PSU, though you are pushing it close with that 1050 watter. Try and stay within 80-90% of the PSU's rating, or 840-945W. 250x3+100W puts you close, overclock, especially 7970's, might put you over the limit.

[neflihim]

Yep, its not crashing just really really slow with the 3 cards...basically frozen once it boots.  This is happening even booting into windows as it usually is quite fast booting.  My Mother board is kinda old and the tech specs say it supports quad-gpu in crossfire.  I'm wondering if it is like a pairing issue, maybe it needs 2 OR 4 cards to work not 3.  

I was running the 2 7970's with no issues on a 750W.  So even pushing 300W that's right there. 

I'm undervolting the cards and running 1500 memclock and 1070 core.