Using 2 graphics card in Mid-2010

One 7970 uses all the power from both aux connectors. You have no hope of running two reliably unless you add an additional power supply.

the 5770 uses only ONE aux power connection. Your Mac Pro has two. Install two 5770 the factory way and live happily ever after.

Barefeats.com did a review of a Mac Pro running two 5770, and it was comparable to the new late 2013 low-end Mac Pro. Not quite as good, but you could graph them both on the same scale.

If you have empty HDD bay or DVD drive bay, you can get the power from it with serial ata to molex female and 6pin PCI Express power to molex male cable.

http://monsieurprix.ca/en/video-graphics-cards/1272-6pin-pci-express-power-cable -to-molex.html

http://www.ebay.com/itm/4-Pin-IDE-Molex-to-Male-15-Pin-Serial-ATA-SATA-Hard-Driv e-Power-Adapter-Cable-/251584054693?pt=US_Drive_Cables_dapters&hash=item3a939405 a5

Then buy and use a 450W external PSU.

There are good threads and how tos on MacRumors forum for Mac Pro and Netkas.org

That will give you 2 x 8-pin and 2 6-pin power connectors and works fine. Cables can be messy (use an open PCIe slot cover to feed the GPUs)

> you can get the power from it with serial ata to molex female and 6pin PCI Express power to molex male cable.

Would not and is not recommended, not by eVGA and not by most users, unless you like to cut corners and take chances that is.

Did I see that you mentioned you were using an external 500W PSU? don't see it mentioned, and your photos were all the ways that are to be avoided unless you know for a fact that the cards really aren't going to 'ask' for more watts and just need some any power connectors to see if it 'works' (boots and displays video). And while some 450W PSU are marketed for GPUs that is just because 450W is small, often talking about special flat units that are designed to fit into those spare optical drive bays many have available (and PC cases have an abundance of).

you need 450W PSU. That was just an adapter to go from 6-pin to an 8-pin (1) anyway. You want standard 6-pin PSU cables (4) so you need two more (non-Apple) to go to the PSU you add.

There needs to be at least 4x6-pin connectors, Mac Pro only has two.

http://www.amazon.com/450W-Graphics-Power-Supply-Juice/dp/B001AO4O98/

http://www.amazon.com/FSP-CrossFire-Upgrade-BOOSTER-X5/dp/B002IZE5RE/

and then maybe this if power cable is too short.

http://www.amazon.com/Kingwin-12-Inch-Express-Extension-PCI-01/dp/B004VR7UJM/

This is a risky Y-splitter to go from a 6-pin to 2x6-pin and which would impose risks.

http://www.amazon.com/PCIe-Power-Cable-nVidia-Video/dp/B0051PWFCU/

Extension 6-pin

Kingwin 12-Inch PCI Express 6 PIN Extension Cable (PCI-01)

http://www.amazon.com/Kingwin-12-Inch-Express-Extension-PCI-01/dp/B004VR7UJM/

I like the photo of how to wire up a booster PSU - click to see full diagram - with all the cables.

http://www.amazon.com/FSP-CrossFire-Upgrade-BOOSTER-X5/dp/B002IZE5RE/

http://ecx.images-amazon.com/images/I/61-DyTAR8LL._AA1000_.jpg

A decent PSU for graphic cards has (did I leave it out?) 2 x 6-pin and 2 x 8-pin, all you need and they are the right "type" for any GPU (and you can use an 8-pin to dual 6-pin if you were to need say 3 or 4 SIX PIN power connectors instead).

And no to 'read' you would have to really say so, and there was not.

The 12 Volt power is the ones you want. Half the leads are 12 Volt power and the other half are the returns (grounds) for the 12 Volt power.