Ordered ATI 7950, got Diamond 7970

Discussion in 'Mac Pro' started by TableSyrup, Oct 16, 2015.

  1. TableSyrup macrumors 6502

    Joined:
    May 29, 2012
    #1
    Ok... a bit perturbed here....

    Ordered a ATI Radeon 7950, with two 6 pin power connectors.
    Seller sent me a Diamond 7970, with one 6 pin and one 8 pin

    Mid 2012, 5,1 Mac Pro

    Is there any safe way to run this card? I don't believe there is, but I am checking just in case.
    (I'd like to avoid the need to a separate PSU, so I am not considering that an option, thanks)
     
  2. crjackson2134, Oct 16, 2015
    Last edited: Oct 16, 2015

    crjackson2134 macrumors 68020

    crjackson2134

    Joined:
    Mar 6, 2013
    Location:
    Charlotte, NC
    #2
    As long as it's not overclocked, you can run it just fine on 2 6-pin connectors. I've had my 7970 running like this for about a year and it's flawless. Check with MacVidCards just to make sure there is nothing specific about the Diamond card that I'm not aware of. There's no reason to downgrade to a 7950...
     
  3. h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #3
    Most likely it will be fine (unless you keep running Furmark etc). If you want to run this card more safely, you may consider to share the workload between the two 6 pin source like this post suggest.
     
  4. TableSyrup thread starter macrumors 6502

    Joined:
    May 29, 2012
    #4
    In order for it to run on the two 6's, I need a mini 6 to PCIe 8 adapter correct?
    Not a big issue, I can get one later, and just bridge the sense

    Bigger issue will be power draw on the traces on the backplane board.

    I will bridge and test power draw.

    Honestly, I think I may just run a pair of 8's (well... 6+2's) right off the PSU and quit screwin around. stupid that this was never done in the first place.... easy for me to do... just have to get some connectors, or long cables.
    ^this is probably the long term solution I will resort to... then I could even run my 5770 and the 7970 at the same time.

    I'd have to tally up the total power draw of everything in my system though, so see if the factory PSU can handle it.... otherwise I may just swap the factory PSU for something larger.... rather than adding a second PSU

    I really didn't want to get this far into 'mods'.... but screw it.... I may as well just have at it and be looking at a machine that will last me even longer

    s.... o..... b..... I just wanna keep mixing and editing.... lol
     
  5. MacVidCards Suspended

    Joined:
    Nov 17, 2008
    Location:
    Hollywood, CA
    #5
    If it was from us we do a secret mod that makes 8 pin unnecessary.
     
  6. TableSyrup thread starter macrumors 6502

    Joined:
    May 29, 2012
    #6
    Can you share this with me? Privately if necessary? It's something I should be able to handle without issue (have some SMR's, etc around... a good meter, good digital station, lead free goodies, etc etc etc....)

    unless it is a software thing I could resolve from a mac platform
     
  7. h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #7
    It's hard to reach the 980W power limit in a 5,1, even though you already running dual X5690, that's just 260W max in total. Let's say your 7970 can really draw 300W. There are still 400+W spare. Even though you fully load all optical + HDD bay, they can't even draw another 100W.

    Anyway, you may interested in this post.
     
  8. TableSyrup thread starter macrumors 6502

    Joined:
    May 29, 2012
    #8
    Well, that's no good.

    Bridged the 'sense' so the card would run.

    Opened up the current video project I'm working on and I'm getting over 90W on the 8 pin, just during playback with background render of a multicam edit. I wasn't even getting into intensive work, just what I was in the middle of with my 5770. And this is with proxy media, I can only imagine what original or optimized would do to it lol

    lame

    Notably, and as I already read elsewhere, the card is only allocating 35W of it's draw to the PCIe slot. Also lame. It would be nice if it would get the max 75 from there. That would significantly reduce the 8 pin aux draw

    So.... now, I have the option of connecting the 12v's to spread the draw across both aux.... I wonder how well that will work. Hmmmmm.

    Any downside to connecting the aux 12v's?

    This is getting into territory I was looking to avoid. And still may..... Might just return the card and get the 7950, or look more into modding this card, or my machine
     

    Attached Files:

  9. Demigod Mac macrumors 6502a

    Joined:
    Apr 25, 2008
    #9
    On cards that are 6+8 pin but work fine with 6+6 (like the one mentioned in this thread, 980 Ti and Titan X), is the 8 pin really just there for the overclocking headroom? As opposed to cards like the 780 Ti and Titan which are 6+8 pin and will shut off if they are stressed.
     
  10. MacVidCards Suspended

    Joined:
    Nov 17, 2008
    Location:
    Hollywood, CA
    #10
    Somewhere is a thread where I did extensive testing with Furmark.

    Was somewhere above 120Watts on a side before shutoff time.
     
  11. TableSyrup thread starter macrumors 6502

    Joined:
    May 29, 2012
    #11
    That's pretty wild. I don't wanna be drawing that on my backplane traces.

    I bridged the sense, and bridged the 'traditionally' unused 12v from the 6 pin over to the corresponding 12v on the 8 pin.

    Without knowing Apples design, I am presuming that all 3 12v's were used at a design spec of 25w per trace. - the theory of the 12v used was based on the possibility of the unused trace actually being unused , but a trace existing , therefore, better load distribution - though, I doubt that is the case..... regardless

    With sense bridged, and the 12v's bridged, the card was actually drawing more overall (more than just having sense bridged to run the card). This raised draw on the 6 pin side of things, without actually reducing the draw on the 8 pin side.

    So.... this sucks. Unless @MacVidCards wants to share some knowledge with me, I'm thinking I'll just bail on the card.
     
  12. dfritchie macrumors regular

    dfritchie

    Joined:
    Jan 28, 2015
    #12
    What program are you using to get the power readings?
     
  13. TableSyrup thread starter macrumors 6502

    Joined:
    May 29, 2012
    #13
    HWSensors ... or.. well... HW Monitor... not sure what the two name thing is about....
     

Share This Page