Sapphire 5850 + XFX 7870 and Toughpower 600W PSU

[Moebius327]

Hello,

I am new to mining and probably this will sound weird.

My current 'build' is this:

CPU: AMD Phenom 9950 Quad-Core Processor 2.60 GHz
GPU: ATI Radeon HD5850 Sapphire (Using 2 x 6-Pin)
MB: Asus M2N-SLI Deluxe (http://www.asus.com/Motherboards/M2NSLI_Deluxe/)
PSU: Toughpower 600W (http://www.thermaltake.com/products-model.aspx?id=C_00000973)

Today I was given a XFX 7870 (needs additional 2 x 6-Pin)

My question is: The PSU has only 2 x 6-Pin (75W) Can I use Y-adapters (2 x 2 Molex - 6-Pin) to power up the second GPU (XFX 7870) or do I have to change the PSU.

Thanks!

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[Moebius327]

Is it better to use 8Pin to 2 6Pin PCI-E Adapter cable?

[ssateneth]

I would just snag some PCI-E power splitters.

http://www.ebay.com/itm/290778077889?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Running gfx cards off a molex is bad. It's too much load on that single 12v. Thats why PCI-E has 3 12v and 3-5 grounds. I own about 26 of them in my basement mining rigs, never had a problem. Last time I used molex for my gfx cards, I melted the wire and the modular connection at the power supply and killed the port, and that was with only 2 radeon 5850.

[Moebius327]

I would just snag some PCI-E power splitters.

http://www.ebay.com/itm/290778077889?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Running gfx cards off a molex is bad. It's too much load on that single 12v. Thats why PCI-E has 3 12v and 3-5 grounds. I own about 26 of them in my basement mining rigs, never had a problem. Last time I used molex for my gfx cards, I melted the wire and the modular connection at the power supply and killed the port, and that was with only 2 radeon 5850.

So I should split the 8-pin (150w) to 2 x 6 pins?

http://www.ebay.de/itm/PCI-E-Y-Stromkabel-2x-6-PIN-8-PIN-Grafikkarten-Adapter-Kabel-PCI-Express-pol-/230916201112?pt=DE_Computer_Sonstige&hash=item35c3ad9a98

Thanks!

[ssateneth]

That item is the wrong thing. That adapter has 2 6 pin input and 1 8 pin output. You want the opposite.

[Moebius327]

Thanks

[Moebius327]

How about this:

http://www.amazon.de/Internes-PCIe-Strom-Verteiler-Kabel-6-polige-2-poliger-Grafikkarte/dp/B003T7071I/ref=sr_1_3?ie=UTF8&qid=1369688937&sr=8-3&keywords=y-kabel+pcie

[bcpokey]

I would just snag some PCI-E power splitters.

http://www.ebay.com/itm/290778077889?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Running gfx cards off a molex is bad. It's too much load on that single 12v. Thats why PCI-E has 3 12v and 3-5 grounds. I own about 26 of them in my basement mining rigs, never had a problem. Last time I used molex for my gfx cards, I melted the wire and the modular connection at the power supply and killed the port, and that was with only 2 radeon 5850.

Holy god, I'd be much more worried about that than molex->PCI-E. 6-pin PCI-E is designed to transfer 75W, 8pin is designed to transmit 150W, 1x75 -> 2x150W seems like a bad idea.

I've run a number of cards off 2xmolex->1x6pin and never had any problem. I suppose YMMV.

[Moebius327]

How about splitting the 8 pin?

[ssateneth]

How about this:

http://www.amazon.de/Internes-PCIe-Strom-Verteiler-Kabel-6-polige-2-poliger-Grafikkarte/dp/B003T7071I/ref=sr_1_3?ie=UTF8&qid=1369688937&sr=8-3&keywords=y-kabel+pcie

This will work great.

Holy god, I'd be much more worried about that than molex->PCI-E. 6-pin PCI-E is designed to transfer 75W, 8pin is designed to transmit 150W, 1x75 -> 2x150W seems like a bad idea.

I've run a number of cards off 2xmolex->1x6pin and never had any problem. I suppose YMMV.

  I guess you never actually tried them, judging from your theoretical "OMG IT WONT WORK". Like I said, I own over 25 of them. Worst case scenario, the plug at the adapter's female end gets a little warm, but nothing horribly dangerous. I've daisy chained them before too, but load balancing needs to be kept in mind then. The PCI-E 6 pin is grossly under specced. This is why the spec doubled the load on the 8 pin by only adding 2 more grounds. The 12v wires remain at 3.

A little googling around revealed the maximum power spec from a molex is 11 amps per pin, so at 12 volts, the 4 pin molex is specced for 132 watts (This doesn't mean if a molex line has 4 plugs you should run over 500 watts through it. This is 132 watts MAX for the entire line). PCI-E has triple the 12v and even more grounds. You should be able to draw 30 amps, or 360 watts, with little problem.

If you need proof to what happens when you overload a line of molexes, this is what happens. This was with ONLY 2 radeon 5850.