Hi! I just opened this thread to examine the possibility of installing a second power-hungry gpu on a 2010 MacPro... So i found this cable: http://athenapower.com/product/converteradapter-cable/pcie-converter/cable-ypcie628 Note: the 6-pin power cable transfers 75Watts and using this splitter i can pull a maximum of two 8-pin connectors=300Watts from this plug. And i want to use it to add a quadro k5000 or maybe a quadro 6000 (windows only) to my existing computer... Now given that the PSU is about 980Watts i can say that the current power consumption is as follows: -two Xeon cpus X5650 with total power consumption of 190Watts maximum -seven sata devices (hdds and a dvd drive) which assuming that consume 15Watts each (which is more than they actually need) gives us a 105Watts power consumption, so 295W so far -a quadro 4000 GPU (requires one 6-pin cable) which (according to nvidia) consumes 150Watts Max, so 445W so far -lets say that the motherboard itself (rams and fans and onboard devices) consume 150Watts more (again this value is a lot more than a motherboard and 3 fans would consume) we have a total of 595Watts (say around 600Watts) So this leaves another 380Watts of PSU power untouched. Which leads me to thinking that i could add one more Power-Hungry GPU in there... (a 300Watt gpu would theoretically be ok to install) But as mentioned the psu only has two 6-pin pcie slots... (and one of those has already been connected to the Q4000) Normally i would assume that the PSU itself can actually power the additional card too, but the mini 6-pin slot comes from the motherboard directly So a) Are my so far calculations okay? b) Is there a chance that i ruin my motherboard if i pulled 300Watts (more or less) from a connector that theoretically is capable of delivering only 75? (if i could directly pull it from the psu maybe it was ok but i am afraid i may damage the motherboard...) Apple says that the 2 x16 pcie slots can deliver maximum 300Watts in total (including the 2 apple's 6-pin external pcie power supply) Thanks a lot for taking the time to read and reply to this question ps. this is my first thread on the macrumors forum.