Dual 4870's in a new MacPro? Why?

Discussion in 'Mac Pro' started by rwdds, Jul 17, 2009.

  1. rwdds macrumors member

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    Philly
    #1
    I had been recounting my experience in an earlier thread (http://forums.macrumors.com/showthread.php?t=747826] ("Need a good laugh?") Several responders asked why buy the 2nd 4870?

    In the last 2 weeks before my MP shipped, I've asked 3 Apple Geniuses at Apple stores and Apple Tech support about running dual DVI 23" Cinema Displays with 4870's. They ALL said I would need a second card. When I attempted the install, there were only 2 power cord clips on the back face of the main board. Both being used by the onboard Radeon 4870. What to do next? Another call to Apple support offered me a nice Indian girl who I could not really understand. Finally, I called a local non-Apple shop that I frequent for hardware and service issues. The very nice service tech told me to take the 2nd card back, since that original 4870 will drive 2 monitors perfectly, in my case, with a simple Mini DisplayPort to DVI adaptor for the 2nd 23" display.

    Can anyone confirm this? And it brings to my mind, how would you install any 2nd graphics card, if a 4870 takes up both power clips?
     
  2. justflie macrumors 6502a

    justflie

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    #2
    I can't speak to if it will drive dual 23" monitors but my strong hunch is a yes. As to power, I believe people have been drawing the extra power from either a SATA bay for the harddrives or the 2nd optical drive bay. You have to buy some cables to make the hookup.
     
  3. Gymnut macrumors 68000

    Gymnut

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    Apr 18, 2003
    #3
    Yes the 4870 can power dual monitors with the use of the Apple mini display port->DVI adapter.
     
  4. IronFixXxeR macrumors member

    IronFixXxeR

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    Jun 20, 2009
    Location:
    Austin, Texas
    #4
    Wow that is pathetic that the Apple employees didn't realize that all you needed was the mini dvi to regular dvi adapter. Unless of course the two 23" screens would be too much screen space for it to drive which I highly doubt. I bought one of these adapters for my 4870 to run a 19" widescreen in conjunction with my 24" main screen.
     
  5. rwdds thread starter macrumors member

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    #5
    It is really frustrating to get incorrect information from the tech people at Apple. In fact, after a few more calls locally and a tech support connection with an Apple supervisor, indeed the Radeon can drive 2 monitors in a dual display setup with just the use of a $29 adaptor.

    Now I just have to find a decent used 23" on ebay or CL...
     
  6. Freyqq macrumors 68040

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    Dec 13, 2004
    #6
    all I know is that on the PC end, a 4870 is ample to run 2 23" screens. I assume that it would work fine?
     
  7. admanimal macrumors 68040

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    Apr 22, 2005
    #7
    A single 4870 or GT120 can support dual 30" displays...so dual 23" should be no problem.
     
  8. goMac macrumors 603

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    Apr 15, 2004
    #8
    I run two 23" Cinema Displays off a GeForce 8800. You'll take a performance hit, but it's not the end of the world.
     
  9. OZMP macrumors 6502

    Joined:
    Feb 18, 2008
    #9
    I can not believe the incompetence of apple staff.

    a few times i have been making quick purchases and fixed basic tech issues for customers who were being ignored, I also couldn't get a job with Apple(in a tech role), yet the local store is full of ********s who know NOTHING(genius and front of store) about the products, no tech knowledge etc but also did not know the basic specs, and me being the rude person I am when i overheard them not knowing always interrupted and filled the client in, prob got them a sale. Oh well now i work for the enemy(in a tech not sales role) :p
     
  10. hehejames macrumors member

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    Jun 9, 2009
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    NYC
    #10
    Apple Genius(es) aren't so much Genius(es) after all.

    I had an experience visiting a store and asked... hey do you have the 4870 or 285 in stock or any video card for the MP? Genius replied... You can't add or change the video card on your own. It will void the warranty :confused:

    They need a new title!
     
  11. hehejames macrumors member

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    NYC
    #11
    What performance hit are your referring to? I had a 30" ACD and a 24" attached to the 8800 at home and it flied all the time!
     
  12. OZMP macrumors 6502

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    #12
    I call them **** heads, don't know about you...
     
  13. bozz2006 macrumors 68030

    bozz2006

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    Location:
    Minnesota
    #13
    for sure, the real apple geniuses don't work in the stores, they post on these boards. for real.

    edit: not that it should take an apple genius to know that the card can drive two monitors. apple geniuses indeed!
     
  14. Chad H macrumors 6502a

    Chad H

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    #14
    What performance hit are you referring too?
     
  15. admanimal macrumors 68040

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    #15
    I can't speak from experience but technically with one video card driving two monitors, its frame buffer (video RAM) is shared between the two, but with two cards each monitor has its own RAM. Of course with just normal app windows this won't make much difference but if you have a lot of OpenGL windows around, it might.
     
  16. Chad H macrumors 6502a

    Chad H

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    #16
    I wonder if it would matter in windows while gaming? Or in Cinebench while running the open GL test? I know in Windows when I play Left 4 Dead it plays on my main monitor(right) and the left shows the desktop or the wallpaper more or less.
     
  17. kellen macrumors 68020

    kellen

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    Seattle, WA
    #17
    Only problems I have had while gaming with two monitors are that if you put it on full screen it blacks out both screens and you can't use the other one. Minor annoyance, but its tolerable.
     
  18. admanimal macrumors 68040

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    #18
    I don't think many games at all support dual screens. The only one I can think of that probably does is Microsoft Flight Simulator (and maybe X-Plane too?).
     
  19. Chad H macrumors 6502a

    Chad H

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    #19
    No, I'm not talking about dual screens. I'm saying if you are running the game on one screen while the other is idle or showing wallpaper of the desktop is their a performance hit at all?
     
  20. admanimal macrumors 68040

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    #20
    If the other screen is showing anything at all, then it is using some of the GPU's VRAM, so in theory there could be a performance hit.
     
  21. Chad H macrumors 6502a

    Chad H

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    #21
    Wow, I didn't know that. I wonder how much? I mean in let's say "Left 4 Dead" it wouldn't matter that much. But if I play Crysis, I'm sure it would affect it a little or in F.E.A.R. 2.
     
  22. Chad H macrumors 6502a

    Chad H

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    #22
    Oh one more thing, is their a way in windows 7 to shut the second monitor off completely w/o unplugging it? That way it would eliminate any performance, again if their is any.
     
  23. admanimal macrumors 68040

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    Apr 22, 2005
    #23
    Well if your 2nd monitor is displaying a 1900x1200x32bit desktop, that's only about 9MB of VRAM. So I wouldn't imagine there would be more than a 1 or 2 FPS difference.
     
  24. Chad H macrumors 6502a

    Chad H

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    #24
    Its Windows 7RC 64 bit. I'm too lazy to boot over to see if I can manually cut the 2nd monitor off. I might disconnect it anyway. Considering I bought this card to game on windows its sucks to take any hit. :eek:
     
  25. rwdds thread starter macrumors member

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    Jan 5, 2005
    Location:
    Philly
    #25
    All good comments and questions about potential performance degradation with 2 monitors. As soon as I find a decent 23" cinema I'll do a few benchmarks and post. Interesting that at the Apple store in Cherry Hill (strangest lookin' dudes I've ever seen in any of the stores!) the very first sales rep who I walked up to, knew instantly about the 4870's dual monitor capability. I was returning the 2nd card and picking up the mini-DP to DVI adapter. The guy was very apologetic and took great care of me.

    Just to add a little more fuel to this confusion, I had called AMD tech support last week while doing my research, and THEIR SUPPORT REP told me specifically, the 4870 would only support one monitor! Go figure.
     

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