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PCIe Splitter cable?

michael pastras

macrumors newbie
Original poster
Jun 3, 2013
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:

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 :(

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.

michael pastras

macrumors newbie
Original poster
Jun 3, 2013
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...)
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