Light Peak and External GPU's

Discussion in 'MacBook Pro' started by Capt Underpants, Feb 22, 2011.

  1. Capt Underpants macrumors 68030

    Capt Underpants

    Jul 23, 2003
    Austin, Texas
    For those Macbook Pro users wanting CUDA support, or those Macbook Air wanting to game:

    Could two light peak ports be utilized to connect an external GPU?

    Is it technically possible?
  2. alust2013 macrumors 601


    Feb 6, 2010
    On the fence
    I'm not sure. It sounds feasible, but we'll probably have to wait for the official specs to come out to find out whether it will really work or not.
  3. simsaladimbamba

    Nov 28, 2010
    Lightpeak will not be fast enough to utilise the full GDDR 3/4/5 bandwidth requirements anyway, as 10Gb/s is slower than even DDR1 memory offers.


    Btw, 1 Byte (B) = 1 Bit (b), therefore 1GB/s = 8Gb/s, ergo 10Gb/s = 1.25GB/s (theoretically).
  4. Erasmus macrumors 68030


    Jun 22, 2006
    Hiding from Omnius in Australia
    Which means it's OK for CUDA, but terrible for games.

    A well designed CUDA program will not use main memory, and will only use the VRAM on the GPU. Which means the transfer to and from the graphics card is mostly irrelevant.

    RAM bandwidth also is a poor comparison, as bandwidth should be compared with PCI x16, which is 8 GB/s; 6.4 times faster than LP. So still slow, but hardly insurmountable.
  5. holmesf, Feb 26, 2011
    Last edited: Feb 26, 2011

    holmesf macrumors 6502a

    Sep 30, 2001
    The memory you're talking about is resident on the video card, and hence the traffic would not travel over lightpeak. What you should be comparing it to is PCI-e bandwidth, not memory bandwidth. PCI-e bandwidth is still much higher than lightpeak bandwidth, but at least it's not hundreds of times higher.
  6. LunaC macrumors member

    Feb 26, 2011
    Yes (even external processors could made to work if the workunit is correctly designed).

    Asus even has a rudimentary one that worked over expresscard, but never made it to market. Actually the main reason TB excites me (well also to fill the eSata gap)

  7. macmac88 macrumors member

    Feb 7, 2011
  8. aznguyen316 macrumors 68020


    Oct 1, 2008
    Tampa, FL
    EXACTLY!! I was going to post this. The user above, although the NUMBERS are true, don't dismiss being able to utilize a GPU externally as not possible for gaming. If an express port can do it (and do it well) then the light peak will be even better.

    If you venture over to notebook review forums or just google "ViDock", PLENTY of people use this method. They hook up 4850's etc and powered via external PSU + express card slot and rock some games hardcore! I mean the cost of some older ATI 3850 etc is fairly cheap and you can be gaming with the new i5/i7 with the amazing CPUs + a desktop card. Even if you lose a good chunk of bandwidth you'll still be doing pretty damn well for yourself. Perfect for a 13" user like myself OR even a base 15" i7.

    I'm really excited for this and hope something is figured out soon... it would be great.

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