Mac Pro 5.1 x2 6870!!!

[redarc]

Hello , i'm wondering if someone can help me made this crossfire x under windows...if someone done it?.. if i have watt for do it? , and more what i have to buy... power cable.. y splitter? if is possible.

Thank you for everything very nice forum!

p.s : sorry for not very well english!

 

[Cindori]

Should be no problem, but you need an external power supply.

 

[redarc]

mhh

so the internal psu its not enough for it? i have a x2 processor board? does it have better psu? i have read about x2 5870.. but i don't think i'm able to do it its not easy..

 

[Toumak]

The psu can handle it, but Apple gave us only 2extra pci-e power connectors
=> you will need 4 of those to power 2 6870

 

[lemonade-maker]

You should be able to use two pcie power spitters. Link

 

[Cindori]

You should be able to use two pcie power spitters. Link

we don't know the ratings of the pcie power rails on the motherboard, so thats not wise.

 

[lemonade-maker]

we don't know the ratings of the pcie power rails on the motherboard, so thats not wise.

Power rating of the rails is probably less of a concern than if the PSU can supply enough current.

Apple claims no more than 300 watts for all pcie cards. One 6870 comes close under load. This is for the pcie card though, not the power adapter.

Many successfully use the splitter method without problems. Link

 

[The-Pro]

Considering the PSU is 950W, im sure it can handle two 6870's. Using splitters on the 6pin connectors is not wise like cindori said because you could destroy the motherboard if it tries to supply more power than what it made for.

"Apple claims no more than 300 watts for all pcie cards." I presume that comes from the fact that the PCIe slot can supply 75W. Times that by 4 (4 PCIe slots) will equal 300W.

I personally wouldn't risk destroying my motherboard (which would be like a $900 repair) if I could use an extra PSU, despite it being ugly and there being more cables.

 

[Toumak]

The Mac Pro are build to deliver 75W by PCI-E power connector
=> you only have 300W (2*75W by the PCI-E power connectors + 2*75W by the PCI-E bus) to power 2 6870 under full load, that's really not enough, and you have a high risk to damage the motherboard ...
As said by Cindori, the best bet is to use a second power supply, which you can put in the second empty optical bay (like the VisionTek or FSP X5 450W)