Multiple Graphics Cards - G5 Quad

Discussion in 'PowerPC Macs' started by MisterKeeks, Jan 20, 2016.

  1. MisterKeeks macrumors 68000

    MisterKeeks

    Joined:
    Nov 15, 2012
    #1
    I would like to get three monitors working in my G5 quad, so I'll need 2 graphics cards in it. I plan to get an FX4500 for the x16 slot. I will either get another FX4500 or use the current 7800GT in the x8 slot. My questions are:
    1. Can the quad power two FX4500s or one FX4500 and a 7800GT?
    2. Would the performance of the 7800GT be roughly identical to an FX4500 in the x8 slot?
     
  2. rawweb, Jan 20, 2016
    Last edited: Jan 20, 2016

    rawweb macrumors 6502a

    rawweb

    Joined:
    Aug 7, 2015
    #2
    Unlike the later Mac Pro, the Quad Core G5 only carries one PCIe aux power port. So you won't easily be able to power another FX4500 which requires the PCIe power. You might be able to convert and run some cables from drive bays down there, but it's probably not worth the trouble. The GeForce 6600 was the stock card which had a max resolution of 2560x1600 on one of the DVI ports. That can plug into an available PCIe slot without additional power..
     
  3. MisterKeeks thread starter macrumors 68000

    MisterKeeks

    Joined:
    Nov 15, 2012
    #3
    Ok. I imagine that I can split the aux power, but I question whether or not the power supply is enough.
     
  4. rawweb macrumors 6502a

    rawweb

    Joined:
    Aug 7, 2015
    #4
    I wouldn't advise doing that. You might shortchange one of the video cards with insufficient power and do some damage. Is there a reason you want another FX4500? The card I mentioned would be more than enough to drive an additional display.
     
  5. MisterKeeks thread starter macrumors 68000

    MisterKeeks

    Joined:
    Nov 15, 2012
    #5
    That's why I'm asking, I'm wondering if someone can definitively state whether or not this is possible.

    I want another FX4500 to max out the quad.
     
  6. rawweb macrumors 6502a

    rawweb

    Joined:
    Aug 7, 2015
    #6
    I don't see how OS X will utilize two FX4500 cards for any foreseeable advantage and splitting the aux power cable is not advisable as you can easily overdraw and burn out a fragile 10+ year old power supply or logic board. However, you could run an external power supply much like folks do with the Mac Pro to bring in another FX4500. There are threads all over the mp forum that might help you in that regard. But if your dedicated to the idea..Like I mentioned earlier, you might be able to steal power and jury-rig from the superdrive and one of the hard drive bays (if you're not using them) to power another 4500. FYI, the card has a maximum power draw of 109 watts. If you can find away to power that, you're good to go.

    Still, the other card I mentioned would allow you to drive your third display and doesn't require additional power. It is the easiest option.
     
  7. ReanimationLP macrumors 68030

    ReanimationLP

    Joined:
    Jan 8, 2005
    Location:
    On the moon.
    #7
    You should in theory be fine splitting it, however like Rawweb says, I wouldn't on a computer that old that's going to be hard as hell now to get working parts (and it's pretty pointless TBH to have two FX4500s).

    Each PCIe slot will supply 75w of power to the GPU, the connector would supply the rest. 6-pin PCIe connectors are rated for 75w of power, 8-pin PCIe connectors are rated for 150w of power. So splitting it would technically fall still within 75w, but again, I wouldn't personally risk it for no real gain.

    With how few Quad G5s were made and such, and how many probably were e-cycled / scrapped / trashed / LCS went kaboom, finding good and working parts is going to continually be harder and harder. Move at your own risk.
     
  8. Surrat macrumors 6502

    Surrat

    Joined:
    Jun 20, 2014
    Location:
    United States
    #8
    According to apple, the pcie slot section of the Quad is rated for max 200 watts with all slots, including the power cable.

    That means two 7800gt or two fx4500 will overload it.
     
  9. tevion5 macrumors 68000

    tevion5

    Joined:
    Jul 12, 2011
    Location:
    Ireland
    #9
    Well it just so happens I ran my G5 quad with two 7800GT's for several months last year. I recently replaced them both with one FX4500.

    But basically I put one in the 16x slot, and one in the 8x slot, then using s PCI-E power splitter, I connected both to external power. This is absolutely needed as the card without power will perform at less than 50% of its capacity with half the frame rate in 3D applications.

    Surprisingly, the 16x or 8x slot made no difference at all. As long as the card was powered they would both work at optimal capacity with no difference between the two. I ran games like Battlefield 1942 @ 1680x1050 with zero performance drop on the 8x card.

    So basically as long as you power both cards, there is no problem having two active at the same time.
     

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