Precise instructions for getting x2 ATI Radeon HD 5870's in your Mac Pro (2009-2010)

Discussion in 'Mac Pro' started by blackwoodfx, Jan 9, 2011.

  1. nanofrog macrumors G4

    May 6, 2008

    Not really.

    The problem isn't with getting power to everything, but the data signals wouldn't be connected as you're talking about power adapter ends only.

    Now if the SATA connection is via a 3rd party SATA card, then you could just string various power adapters together, and run a SATA cable from the card to the SSD. Unfortunately, you'll likely have issues getting one that will boot OS X (presume you don't already have one that does).

    Making your own adapter:
    There are easy ways to connect the wires, so there's no need to panic. Wire nuts, crimp connectors (butt splice; pic is for illustration - you can twist 2 wires together for one end, and use a single wire in the other <cut this end longer, and fold it over so it crimps properly> - I'd recommend using the blue one if you go this route) are a couple of ways. The reason for folding the wire, is the gauge is likely too small for blue (expect the adapter wiring will be 18 AWG, and blue is meant for 16-14AWG).

    Another, and easier method, is to use tap splices (no cutting of the wires on the Backplane Extension cable at all; downside is they're bulkier once you get it all assembled).

    You should be able to find these connectors locally with little to no hassle (i.e. auto parts or hardware stores carry them).

    BTW, you'll want a pair of crimp pliers if you use butt splices (additional information in the link, which I'd recommend reading).


    Take a look at this article, as it has some performance data on the GT120.
  2. strausd macrumors 68030

    Jul 11, 2008
    So how well do you think the GT 120 would do in handling some non intensive windows? For example, my main program is Autodesk Maya and I would like to keep my viewport on the 5870. Then I would like to have my outline, light linking, and UV texture editor on the GT 120 if possible. I also may have the render view on it too, but it would be through Mental Ray. Would there be any problems with having these windows running on the GT 120? I just need to make sure these windows won't be any noticeably slower. And having multiple windows of a single application on two GPUs wouldn't limit the performance, correct?
  3. nanofrog macrumors G4

    May 6, 2008
    If I understand you correctly (windows that generate a load on the GPU will be on the 5870 only), then you might manage with what you're trying to do (not used the GT120 myself, so I'm hesitant to say for certain it's 100% fine for what you want to do, as it's a budget part = low-end performance vs. other GPU's released at the time).

    The 5770 is a much better card though, and would be able to handle this sort of usage.

    If you have access to a free or very inexpensive GT120, you could try to test it out (cheap enough = not a major loss). Otherwise, go for the 5770 + 2nd PSU to feed it as previously discussed.
  4. fairlane32, Nov 25, 2011
    Last edited: Nov 26, 2011

    fairlane32 macrumors newbie


    Nov 25, 2011
    Can't get Crossfire to work?

    Hi everyone,
    I'm wondering if you gentlemen can help with me getting Crossfire to work on my Mac pro (mid-2010) with two AMD 5770's. I have the two GPU's installed, 3gb of ram, windows 7 Enterprise x64 bit on Bootcamp, a Powercolor crossfire bridge (from and the latest Bootcamp drivers from AMD's website which can be found here:

    After installing the 2nd card (in slot 2, each card slot is a pci-e x16 slot I believe) and booting into windows, I can log in fine, but launching the CCC and enabling Crossfire BSOD's my system. I can't figure out why.. I only have one monitor (Samsung SyncMaster P2770 connected to the slot 1 gpu using DVI) and Device Manager sees both gpu's, and CCC reports both a primary gpu, and a disabled gpu, (i'm assuming because crossfire isn't enabled). If I reboot the system after the BSOD, it will load windows fine and I can log in, but as soon as the CCC tries to load in the system tray the system BSOD's again. I have had to boot into safe mode, prevent CCC from starting when windows starts, reboot the system and windows logs on fine. I can then manually launch CCC and see that crossfire is of course not checked off. CCC also warns, when enabling Crossfire, to keep the Catalyst A.I. in the Standard position due to application and display corruption issues. I have left mine in the Standard position.

    I have also tried totally uninstalling all of CCC's components and used the windows CCC package dated 11/15 (v11.11) as of this posting, but that didn't work either (same results).

    I was able to ask Apple over the phone whether Apple "officially" supports Crossfire in a Bootcamp environment, otherwise I would be more than happy to either return the 2nd 5770 or use it as a back up if the primary one dies..
    The tech did some research and emailed me a .pdf of Crossfire - but it was simply an explanation of what Crossfire was, no reference to it working in a Bootcamped system.

    I've read other folks in a similar system setup (but not exactly like mine) have gotten crossfire to work but I can't seem to get it to.

    What am I doing wrong?
    Am I using the wrong bridge? bridge

    Any help would be appreciated.. I hope everyone had a wonderful Thanksgiving

  5. umgoblue2008, Dec 19, 2011
    Last edited: Dec 19, 2011

    umgoblue2008 macrumors regular


    Dec 6, 2008
    "3. Next, you need a SATA power adapter to go from SATA to 4-pin molex. This is necessary to switch the 5.25" PSU on and off, as you turn on and off your Mac Pro using the main power switch. Without it, the PSU will not self-start.

    6. Finally, you'll want a SATA splitter to allow that 4-pin Molex to SATA cable enough length to connect back to the Mac Pro SATA cable assembly.

    From the back, connect the 6-pin 12V graphics card cables to the PSU. Also connect the SATA to 4-pin Molex adapter and then connect the SATA power splitter to that and the other end of the SATA power splitter to the second slow of the existing Mac Pro SATA cable. Go ahead and snap off one side of the SATA splitter cable lock to make the fit. Just push hard with your thumb and it will easily pop."

    Why not just connect straight from the 2nd slot Mac Pro SATA to the 4 pin molex on the PSU via:

    Male SATA to Female LP4 Molex Power Adapter Cable, 6 Inches

    Will this work? Or am I off base, thanks.
  6. shissler1987 macrumors newbie

    Oct 13, 2011

    I m running a mac pro 2010 with xeon w3680 and 2x ati 5870, 32 GB Ram, 3 hdds and 3 ssd wirh an apricorn 4x ssd pci e card ... taking the power from the two dvd drives for the 2nd gpu and every thing works fine... the mac pro doesnt take more than 600 W and doesn t crash...

    I tested that system for more than half a year now with a lot of Battlefield 3 ... and of course it still works ... Why shouldn t it work?

    there is NO reason for a 2nd psu ... at all ... would just be a waste...

    You just have to do tha math...
  7. nanofrog macrumors G4

    May 6, 2008
    It's based on math.

    But there's more to it than just adding the power consumption figures of the added equipment to those the system already consumes (before installation of the new gear), and making sure it doesn't exceed the nominal rating of the PSU (you even have to be careful and make sure you realize what that figure is, as it's more common for manufacturers to list the peak value rather than the nominal one, as it's larger).

    As to the specifics, it has to do with how PSU's are actually made, as most don't use a single rail for the +12V source (some do, but the MP uses multiple rails), so you're not drawing too much power from any specific rail. Then there's wiring and PCB trace power loads to consider as well (there has to be sufficient cross-sectional area in order to safely allow the current being drawn to pass without over-heating, and potentially starting a fire).

    You've been lucky so far, and I suspect you haven't actually pushed the GPU's to their full power draw with how you're using them (= haven't over-drawn either a rail or PCB trace). That's wonderful, and if you want to continue with your existing configuration, great.

    But there is a safety factor involved here, so I'd recommend learning more about this before recommending something that could not only damage their systems, but even potentially start a fire.

    There is at least one thread in here where what I'm describing has actually happened; too much power was drawn over the PCB traces on the logic board which shorted, causing the logic board to die. And replacement parts for MP's aren't cheap (i.e. new logic board for a MP typically exceeds $800USD, unlike a typical PC where the boards can be had for quite a bit less).
  8. ClassObject macrumors 6502


    Mar 1, 2010
    Anybody here ever burn a pcb trace with a video card ( or two )? I seriously doubt it's happened. I suspect the PSU is the weak link. I'd love to hear real true stories. Especially considering all the hype about burning PCB traces on this board.
  9. nanofrog macrumors G4

    May 6, 2008
    It's in here somewhere.

    To give a bit more detail, the logic boards are HAL (Hot Air Leveled = copper traces are covered in a thin layer of solder). When too much current is drawn, they heat up, and it can actually melt the HAL, and short.

    The case I mention did precisely this, and the logic board had to be replaced (IIRC, it was a 2008 system).

    Now the reason this is critical, is the PCB traces that carry the GPU power aren't likely over-designed by much, if at all, are due to both physical constraints (available surface area on the board for trace routing), and cost reasons (can't push the copper weight of the entire board to increase the current capacity of just a few traces). BTW, the 6 pin connectors are specified at 150W (PCI-SIG's PCI-Express 16x 150W-ATX specification, v. 1.0).

    Now consider the following: Power = Voltage (V) * Current (I).

    So working backwards, you get 150W = 12V * I, so the current, symbolized by I, you get I = 12.5 Amps.

    Assuming the copper is 2 oz. (max you'll see in a computer), is open air (on an outer layer), and will see a 30C rise in temp, the trace width is 2.51mm (IPC-2221 spec). It's worse if it's an internal trace (goes up to 6.54mm since it can't cool itself).

    Take a look here, and play with the copper weight at 0.5, and 1.0 oz, just in case they went thinner (wouldn't expect 0.5oz, but 1.0oz isn't out of the realm of possibilities if they were really aggressive in cutting costs after the shift to Foxconn for board manufacturing, which began with the 2009 models).

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