I started a thread that I powered two down-clocked HD7970 to beat Mac Pro 6.1 3 years ago. At that time I used only dual on board 6 pin to dual 8 pin + 2 sata -> dual 6 pin for the 2x HD7970. It works because those two cards were down-clocked. 3 years later, I still see full potential of the machine (since 2009) that can beat nowadays' Hackintosh in this small, cute, military grade, Mac Pro tower with triple Titan X. Mac or Windows wise. If Volta won't be available for Mac Pro any time soon (I still hope it will), this is probably the most powerful setup we can get. System: Mac Pro 5.1 (2010) Dual X5690 3.46Ghz 96GB RAM 1333Mhz Titan X Pascal Titan X Maxwell GTX 1080 Ti 1 bootcamp 256gb in optical drive space, 1 ssd MacOs 10.12.4. Without spinning 3.5" HDDs, Pixlas mod can be safely running 2 Titan X since the mod let the dual cards runs from the 12V rail from the PSU directly. To be able to run additional Titan X, an external power to power the third card is needed. I found xbox 360 first 2 generation PSU (exclude the slim) is easy to work with (203W or 175W). This PSU selling everywhere (gamestop, ebay) for $10-15. And it's easy to work as long as you have a multi-meter, a solder iron, and a few of heat shrinks. So I decided to have it a try. Here are what I did: Open the 980W PSU, make a pair of 125V (AC) and 12V leads. The soldering job took a little time with regular solder iron, like the other guys said in the discussion. But it can be done with patience. This picture shows the 125V parallel pair leads. Here is the Xbox 360 Power supply to put additional 175-203W 12V power to the 3rd GPU. Test it from outside first. Later I put it into the empty optic drive 5.25" space and conceal it nicely. strand all yellow together as +12V, and all black as GND. leave the red (5v) untouched. The blue line is the switch on signal line, when you feed with Mac Pro's onboard 5v, it engage the 12V from the PSU to your GPU. In the photo it shows I used the 5V from the SATA power. Similarly, when you turn off the MacPro, it turns off the extra PSU in such same way. (don't be fooled here, the pink wire here is blue from xbox PSU). Now to put it into the optic 5.25" drive space, I take the xbox 360 power's cover off, unplug the fan of the PSU (I don't need it, and I want it be silent, too). Before put it into the space, make sure you lead the wire from the right side so you get easier to drag the compartment. I did purchase a 5.25" empty plate to fit the PSU nicely (in fact with my bootcamp SSD in the same space as well). View attachment 697805 Up to here. My onboard 12V pool power from the 980W PSU, and the extra 175W PSU is ready. Now there is one magic product I want to share with: the EVGA power link: http://www.evga.com/articles/01051/evga-powerlink/ Amazon selling it $9.99 https://www.amazon.com/EVGA-PowerLi...qid=1493419066&sr=8-1&keywords=evga+powerlink What it does is to provide different angle for your GPU connector. I found it's wonderful because of two things: 1, it transform single pair of 12v+GND to dual 8 pin with internal handling of the pin layout, ie you feed with 12v it give you direct 8+6 to your cards, period. 2, it include power conditioning with two capacitors as shown here: The end result shows a neat cable arrangements. The SSD shown in photo with case taken off. It's easy and securely plugged in. Since Titan xp is too expensive, I have ordered a 1080 Ti coming instead, and I will post update when it runs together with my existing 2 Titan X. Hope you guys enjoy it. You know what, how I wish the next Mac Pro 7.1 use the same case design as mac pro 5.1. It's so much fun with versatility.