Dual 5870's in MP 2009 with Splitters Work Safely

Discussion in 'Mac Pro' started by sarthak, Jun 28, 2013.

  1. sarthak, Jun 28, 2013
    Last edited: Jun 28, 2013

    sarthak macrumors 6502

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    #1
    I just purchased 2x 5870 Mac graphic cards (Apple) and plan on installing them in my 2009 Mac Pro Quad Core. This is part of my upgrade plan, installing two of these along with a W3680 Hex.

    Two years ago, someone uploaded a video demonstrating that two 5870 cards can be installed using 6pin->2x6pin splitters and crossing them to even the load on the cards. [LINK] A year later the same person stated that "No problems so far. My Mac Pro is on between 12-14 hours per day every day and power supply fan just idols along even when under heavy load." Another year has gone by and this person is still using the 2x5870's in their 12 Core Mac Pro.

    So far, I've used a single GTX670 off both power connectors in my QC Mac Pro. I moved away from it due to the lack of EFI. It worked just fine, AFAIK that you can't use a GTX580 / 590 and many other cards without an AUX power supply.

    With the two 5870's I've ordered, people have stated that it is unsafe due to the wattage that the PSU can supply and the tracers on the board. In the case of the aforementioned person, they have been using the configuration for two years at "12-14 hours a day". So does this mean that the theories are false and it's SAFE to use dual 5870's in the Mac Pro?

    Calculation:
    5870 POWER: 188W
    5870 POWER: 188W
    TOTAL POWER: 376W

    PCI-E LANE POWER: 75W
    PCI-E LANE POWER: 75W
    6PIN POWER: 75W
    6PIN POWER: 75W
    TOTAL POWER: 300W

    It appears there is a lack of power that can be supplied and it's not likely that the cards draw MAX power all the time. The biggest question is about the voltage. I've read stories written by fellow members about using two cards, many of those cards include the 2x 4870x2 and 2x GTX580's. Those cards pull almost 500W total.

    Following this [LINK] gets you to a listing where the seller has sold 152 splitter cables. Assuming that only 1/10th of the people are using high power cards, it's possible that this setup "just works".

    The question is still about copper. To avoid damage, one could route a SATA -> Molex as well as 2x 6pin cables out the back of one of the PCI-E slots and plug it into an external PSU. That's the cleanest way of getting an AUX PSU working. I will definitely try with and without the ext. PSU once I receive the 5870s.
     
  2. GP-SE macrumors 6502

    Joined:
    Feb 27, 2013
    #2
    I would NOT risk it. At worst case:
    6pin Power: 75 Watts
    8pin Power: 150 Watt
    PCI-E Slot: 75 Watts

    So the Mac Pro can only provide: 225 Watts MAX (6pin x2, plus PCI-E)

    even with two 8pin adapters max Power would be: 375 Watts (8pin x2, plus PCI-E)

    You can try running splitters, but honestly I would just buy an AUX Power Supply than risk damaging the traces on a $600 Logic Board.

    also the GTX 580 has a TDP of 244 Watts, not 500 Watts. A GTX 590 (dual GPU on one card) has a TDP of 365 Watts. Which is close to the MAX of a 8pin+8pin card.

    http://en.wikipedia.org/wiki/GeForce_500_Series
     
  3. sarthak thread starter macrumors 6502

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    #3
    I was talking about using two cards, each being either 4870x2's or 580's.

    You're right, I presumed it was 150W off each of the 6 pin. Fixed. So the max it can provide would be 300W for two cards incl. the PCI-E slots. This is below the max TDP of 376W on the cards.

    Big mishmash of information in this Apple Support thread.

    I agree that it is safer to use the external PSU. The cleanest method I've found is by routing a SATA -> Molex Cable as well as the 2x 6 Pin Cables out the back of one PCI-E slot and into an external PSU. I'd prefer to stick it in the Optical Drive bay however, it requires a bit of work.
     
  4. TzunamiOSX, Jun 29, 2013
    Last edited: Jul 2, 2013

    TzunamiOSX macrumors regular

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    #4
    i think the problem is not the power supply. Perhaps the traces for the GPU on the Logicboard are to small to handle more then the 7,25 Ampere of a 6 pin Power Cable.

    Also the cables for the optical drives in a Mac Pro 2009+ are very thin.

    A 8-pin or 2 x 6-pin has up to 12,5 Ampere.
     
  5. sarthak thread starter macrumors 6502

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    #5
    This is becoming a bigger issue than I expected. I'm eager to cancel the order for the 5870's and pick up a EVGA GTX680 and flash it. I drive 4 monitors and running them off a single power efficient card would be better. The last card I used was a Zotac GTX 670 and it didn't have EFI which became a big problem with my usage style.
     
  6. jenzjen macrumors 68000

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    #6
    7870 eyefinity 6?
     
  7. sarthak thread starter macrumors 6502

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    #7
    Can't seem to find one that has EFI. The lowest cost option so far is a GTX680 and DIY flash for around $400. Considering the massive problems associated with running 2x 5870s and that I do play games under Boot Camp with Windows 7 (rotate 3 of my displays into landscape in order to get a better field of view) a 680 seems fair.
     
  8. Studio K macrumors 6502

    Studio K

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    #8
    Besides not having an EFI, was the Zotac a decent card?

    What was the fan noise like? How were the temperatures?
     
  9. The-Pro macrumors 65816

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    Germany
    #9
    Read the title and thought ill point you to a person who installed 2x 5870 and has a video on youtube and hes been using it for two years.
    Then i saw u knew about it allready :p

    I would also say dont risk it but then again its been working fine for the youtuber and all devices are made with a tolerence. its said it can provide 75W but maybe can go up to 100W no problem. we cant know this for sure but mostly likely is the case
     
  10. sarthak thread starter macrumors 6502

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    #10
    It was a reference card I picked up from BestBuy for $320 including taxes. In OS X, the card was a silent beast. Drove all four monitors with absolutely zero lag and zero issues. The card "just works" with all the apps I tried including Da Vinci resolve where GTX670 was processing and GT120 was the GUI card.

    I used the card a lot in Windows, with EVGA Precision I was able to set the fan curve allowing it to ramp up and keep temperatures below 55-60c while under 100% load for hours at a time. I always used a headset so I was never bothered with the fans running at max.

    I was just bothered by the lack of EFI, if I ever had issues booting into Windows it would become a disaster switching without EFI. Even the GT120 wouldn't show boot screen because I hadn't gotten into OS X with it once. So this time it's EFI or nothing, best bet so far is a EVGA GTX680 and DIY flash.

    That was the video I saw prompting me to order two 5870's. Considering what I have spent on the machine already, I'll take the safe route. I find sticking in Auxiliary PSU's and running wires all over the place kind of silly, can't believe Apple installed a 980W PSU but didn't provide another set of 6 pin connectors.
     
  11. slughead macrumors 68040

    slughead

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    Apr 28, 2004
    #11
    That is an incredibly bad idea. Please don't do this.
     
  12. Studio K macrumors 6502

    Studio K

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    #12
    I just watched this video recently. I've seen some of his other Mac Pro video's as well.
    He spent a lot of money on that setup. The Mac Pro is a top-of-line 12-core dual-processor model. He's got the two 5870's (not cheap), an Apple factory SSD (512Gb--not cheap) and an Apple Raid card. HE also had 2 Apple factory superdrives. He replaced one with a Blue-Ray drive.
    And then there are the THREE 27" Cinema Displays.

    "And there you have it. The Mac Pro. Truly the Rolls Royce Phantom of desktop computers" (quote from video)
     
  13. derbothaus macrumors 601

    derbothaus

    Joined:
    Jul 17, 2010
    #13
    ^^^ Yeah. A video about someone overbuying underperforming Apple retail kit. Save the money kids. Get 3rd party and blow that royce out the water.
    Apple factory SSD in a word - sucks.
    Apple RAID card in the same word - sucks.
    2 5870's = total power suck for no speed gains.
    OP choose correct for 4 displays. Plus you actually get to have a card 2-3 times faster than the 5870. Dual cards are a sad myth.
     

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