PCIe Splitter cable?

[michael pastras]

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.

 

[MacVidCards]

Try the search bar, this topic has been dealt with ad nauseam

 

[The-Pro]

get an external power supply and be done with it. Much easier and safer

 

[michael pastras]

hmm...
Yeah i've heard of the external psu solution but i would really prefer having the job done internally (if possible, of course).
So i would like to see whether anybody else has successfully done this thing without damaging the computer.
If i don't find a clue then i will probably go with the external psu solution...
(i mean the numbers indicate that the existing psu is enough for the job but who knows what can go wrong...)

 

[ActionableMango]

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?

The answer to that should be obvious. In any case, if you want to research this more, here's a long thread where people recently debated the issues:
https://forums.macrumors.com/threads/1505726/