Power for new video card

Discussion in 'Mac Pro' started by w8ing4intelmacs, Dec 17, 2015.

  1. w8ing4intelmacs macrumors 6502a

    Feb 22, 2006
    East Coast, US

    I have a MP 4,1 with a ATI 5870. I have a GTX 650 that I want to install. If I wanted to keep both, what's the best way to power the new video card? Would this splitter do the job?

    Any advice/comments regarding whether I should just pick one and ditch the other would be appreciated too.

    My ultimate goal is to push 4K content unto my new TV. My understanding is the ATI 5870 cannot handle 4K but I should be able to with the GTX 650. I think the GTX 650 could handle both my computer monitor and the TV but it doesn't support the Apple boot screen. Please correct me if my understanding is off.

    Thanks in advance!
  2. Gav2k macrumors G3


    Jul 24, 2009
    I wouldn't recommend splitting any cable when it comes to powering a gfx card if I'm honest.
  3. h9826790, Dec 17, 2015
    Last edited: Dec 17, 2015

    h9826790 macrumors G4


    Apr 3, 2014
    Hong Kong
    Before you install both cards with internal power only. You better check how much power each card can draw.

    From memory, the normal 650 should draw only 64W. However, apart from few specific cards, they are designed to draw power from the 6pin but not via the PCIe slot. So, the worst case will be all 64W from the 6pin.

    On the other hand, your 5870 can draw about 200W under extreme stress. By considering your workflow should not be running Furmark, and the normal peak is around 150W, you better check how the card draw those power. e.g. 30W via slot, and 60W via each 6pin.

    If the 5870 draw quite a lot of power via the slot. e.g. 70W via slot, and 40W via each 6pin. Then there is a simple solution (with relatively low risk), which is use the splitter to power the entire 5870 from a single 6pin source, and leave the other 6pin for the 650.

    However, if you really run Furmark in this config, the 5870 can easily draw more than 120W via a single 6pin, that most likely will trigger the protection and shutdown your Mac (this may cause permanent damage).

    Besides, if the 5870 mainly draw its power from the 6pins, then it will be harder to achieve that safely.

    So, you better do some tests and find out how your cards draw the power (HWMonitor or iStat can easily get you the required data).

    Here is my sharing about how I power dual 7950 by internal power only. It may give you some idea about how to run a 2x6pin card via a single 6pin source.
  4. w8ing4intelmacs thread starter macrumors 6502a

    Feb 22, 2006
    East Coast, US
    Now you have me scared.

    I'll out some the things you mention when I get home. Thanks!


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