New Titan X physically compatible with older MacPro?

Discussion in 'Mac Pro' started by asiga, Aug 8, 2016.

  1. asiga macrumors 6502a

    Joined:
    Nov 4, 2012
    #1
    Apart from the fact that currently there're no drivers for NVIDIA Pascal GPUs, can you actually plug a new Pascal Titan X into an older (read: non-cylinder) Mac Pro? Would the PSU be powerful enough? Does it have 8+6 pin plugs?
     
  2. h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #2
    Yes, the card can fit in the PCIe slot.

    Yes, the PSU is powerful enough.

    No, the cMP only has 6+6.
     
  3. Synchro3 macrumors 65816

    Synchro3

    Joined:
    Jan 12, 2014
    #3
  4. theitsage macrumors 6502a

    Joined:
    Aug 28, 2005
    #4
    I can confirm what h9826790 and Synchro3 said. The PCIe slot will fit and the internal PSU has enough juice to handle the Titan X. All you need is a 6 to 8 pin power cable - https://amzn.com/B00PVJ2DNC. I've been using a 980 Ti for half a year with no issue.
     
  5. Draeconis macrumors 6502a

    Joined:
    May 6, 2008
    #5
    Personally I wouldn't run a card drawing 250w TDP through a setup designed to provide 225w. But it's your hardware :)
     
  6. Synchro3 macrumors 65816

    Synchro3

    Joined:
    Jan 12, 2014
    #6
    Somewhere here in the forum I read the Mac Pro 4,1/5,1 supports unofficially up to 290 Watt until it switches off the power.
     
  7. h9826790, Aug 10, 2016
    Last edited: Aug 10, 2016

    h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #7
    It depends on how the card draw power.

    AFAIK and base on my own test, each 6pins can deliver up to 120W before the cMP shut itself down.

    And since apart from the RX480, I never heard any card will intentionally draw more than 75W from the slot, due to that's a widely used standard. So, no matter if there is any self protection on the PCIe slot, I still count that we can only draw 75W from the slot.

    So, 120W x2 + 75W = 315W absolute max. But this highly likely will shutdown the Mac at some stage. So, to keep the Mac working, we take 10W away from each 6pin.

    Now, 110W x2 + 75W = 295W, this should be the real world operational max.

    HOWEVER, this is base on the card can evenly draw the power from each 6pin and get the max 75W from the slot.

    In real world, if the card is in 6+8 config. The card may pull power like the following.

    50W from PCIe slot
    50W from mini 6pin A
    120W from mini 6pin B -> 8pin

    The total power draw is just 220W, it's even below the official 225W limit. But due to the uneven power draw. It can still shut down the Mac when the 8pin draw 120W from a single 6pin source.

    Another way to safely power the card is as follow.

    6pin -> 2x SATA (should be 110W limit, but never seen on any official Apple document)
    8pin -> 2x mini 6pin (official 150W limit, real world 240W absolute max, operational at 220W max)
    PCIe slot (75W).

    Technically, this config can power a card that draw up to 335W but still within the official limit. And possible up to 405W operationally.

    Anyway, I did post some of my power draw test result at here.
    http://forums.macrumors.com/threads...or-approaching-silence.1982499/#post-23120938
     
  8. benjaprud, Aug 11, 2016
    Last edited: Aug 11, 2016

    benjaprud macrumors member

    Joined:
    Apr 9, 2015
    #8
    The 6 pins connectors can effectively deliver 10 amps maximum each (about 120 watts) at which point a safety circuit shuts down the PSU. This is meant to prevent the motherboard traces that carry the current from heating, their cross section being too small to carry heavy currents (if you pass too much current through a conductor that's not thick enough to handle the flow of electrons then it becomes resistive, heats up, lowers the output voltage and can end up in fireworks).

    Thanks to this safety there's not much risk going higher than 225W except for shutting down the PSU (which can still corrupt your drive if you're unlucky). By modding the PSU (or drawing current from another source) you can work around the motherboard's power bottleneck and harness a greater output from the PSU which is capable of supplying much more that that (remember it's a 980W capable PSU which is a lot).

    The Pascal Titan X should behave as well as the previous one in cMPs. With overclocking software it can be pushed to 120% TDP which might be enough to trigger the power safety (Maxwell TX is limited at 110%), so you might not get the full overclock potential using the 6 pin connectors.
     
  9. heero503 macrumors newbie

    heero503

    Joined:
    Nov 12, 2014
    Location:
    Hong Kong
    #9
    As I have read all you guy share info and macvidcards, I believe the 8 pin will draw high current than mini 6pin can provide. The most safe method that I use 2x SATA power to drive a 6pin and group the mini 6pins to a 8pin. I started to build the config as above. The HDD mount I bought is WD as I think the electronics part will be more reliable. The SATA connectors are Foxcon! In HK, there is very hard to find and also a good quality cable.

    as suggested:
    6pin -> 2x SATA (should be 110W limit, but never seen on any official Apple document)
    8pin -> 2x mini 6pin (official 150W limit, real world 240W absolute max, operational at 220W max)
    PCIe slot (75W).

    1080Ti is 250W (21A) max (PCIE 75W (6.25A) + 6->8Pin 150W (12.5A) is already 225W and I think 2x SATA (if safe we get 80% of it max) is 80W 6A enough to handle it~

    Only one thing is unknow that how the 6pin share current from 2 SATA port.
    I have tested yesterday, she always draw 1.2xA from HDD Bay3 and most the time 0.5xA to 1.2A from Bay 4 when i Connect to 5770 and full load it.

    If it is work and stable, I will buy the mini 6pin to 8 pin cable from here to make the cabling easier:
    https://www.moddiy.com/products/App...tandard-PCI%2dE-8%2dPin-Video-Card-Cable.html

    For dual SATA to 6pin I will search a good quality one, if there is any suggestion, please let me know~
     

Share This Page