MacBook Pro GPU runs on PCIE 8X lane

Discussion in 'MacBook Pro' started by EdDuPlessis, Nov 23, 2014.

  1. EdDuPlessis macrumors 6502

    Joined:
    Nov 23, 2014
    #1
    Hi all,

    I noticed in the system profiler the GeForce 650M in the Retina MacBook Pro runs at 8x PCIE lane width yet I have also read in some places that the chip is overclocked to 660M speeds. However benchmarks indicate GPUs work best running on 16X land regardless of clockspeed or PCIE version.

    Is there any way to change the MBP's graphic card to run at 16X?
     
  2. leman macrumors 604

    Joined:
    Oct 14, 2008
    #2
    Even if there were a way to do it (even there is no known one, AFAIK), you would not gain anything from it. Even high-end cards gain close to nothing to going full 16x PCIe 3.0 lanes. For a lower-midrange card like 660M, the limit is its own processing ability and VRAM bandwidth. There is not much sense in increasing the system interface speed if the GPU can't consume the data that quickly in the first place.
     
  3. EdDuPlessis thread starter macrumors 6502

    Joined:
    Nov 23, 2014
    #3
    So basically the 650M can't even saturate a 16X lane, right?

    Are all MBP and iMacs running at 8X?
     
  4. leman macrumors 604

    Joined:
    Oct 14, 2008
    #4
    It certainly can saturate a 16x connection, but not for any practical purpose. Basically, you'd need to copy data all the time, without doing anything useful with the data itself.

    At any rate, if you are looking for a no-compromises GPU performance, your only bet is to build a custom machine with a dual 980 or something similar. Nowadays, Macs have quite adequate GPUs (still need to refresh that 15" MBP though), but they are far from being best bang for buck on that front.
     
  5. EdDuPlessis thread starter macrumors 6502

    Joined:
    Nov 23, 2014
    #5
    Thanks for expert advice. Is the card in the top Retina iMac 8X?
     
  6. leman macrumors 604

    Joined:
    Oct 14, 2008
    #6
    No idea :D
     
  7. nerowolfe macrumors member

    Joined:
    Oct 23, 2014
    #7
    Beside gfx chip and OS used, power supply and heat dissipation rate are the two major bottlenecks when it comes to Macbooks' GPU performance.
     

Share This Page