External GPU via Thunderbolt ... Someone explain how this would work exactly.

Discussion in 'MacBook Pro' started by Adamantoise, Aug 24, 2011.

  1. Adamantoise macrumors 6502a

    Aug 1, 2011
    Can someone explain how this would work exactly? I know the new Vaio Z has a docking station that acts as an external GPU but I'm not sure I understand the details.

    Pretty much GPUs today are installed on a slot on the motherboard of the computer it resides in. Will these external GPUs simply communicate all the necessary data along the TB port?

    Wouldn't the external GPU require it's own power supply? Lastly, are there any external GPUs in the works?
  2. Adamantoise thread starter macrumors 6502a

    Aug 1, 2011
    How are those things powered?

    Externally? Or does the TB spec allow for tapping the PSU?
  3. Prodo123 macrumors 68020


    Nov 18, 2010
    There are external GPUs currently in development!

    First, only laptop GPUs are permanent. Desktop GPUs use a standard called PCI Express. You plug a GPU card in the PCI Express slot and boom, it's installed.

    The Thunderbolt is literally an extension of the PCI Express connectors found in desktops. Just like how eSATA is an extension of the SATA ports. So if you plug in an external GPU to the TB jacks, then it's the same as you plugging it into a PCI Express slot.

    TB would carry 10W of power, too puny to power a GPU. So yes, an external GPU would require a separate power supply.
  4. head honcho 123 macrumors 6502

    Dec 18, 2008
    New York
    i would think it would require an external power source. the TB doesn't have enough power to power an external GPU card
  5. L0s7man macrumors 6502

    Feb 26, 2009
    Thunderbolt = PCI-e (8x I think)

    Well, almost. It's kidna like ExpressCard. It is almost like PCI-e. Theoretically it makes it "easy" to do external GPUs and pretty much anything you want. Plugging something via TB is like plugging it to PCI-e slot.

    I'm following ViDock guys; the trouble is they can't get specs/TB chips or anything from Intel. It's rather werid. But they said 2-3 months after Intel ships them the chips, they'll have the early product ready.
  6. dusk007 macrumors 68040


    Dec 5, 2009
    That is not really true. eSATA is the very same as SATA only a different plug, but thunderbolt changes the signal to something different and than back.
    Thus it can be better compared to a SATA HDD that you have in an external USB case. The difference is Thunderbolt is a lot faster with better latency and it can piggy back just about any other protocol.

    You would definitely need an external power sourse. Currently Thunderbolt only supplies 10W. In theory though especially with the optical Light Peak implementations it is definitely possible to supply as much as 75W if they changed the plug a bit. I don't know how much Sony's impl. supplies.
    Any manufacturer of Notebooks could create a somewhat proprietary solution that supplies enough power.
    PCIe is rated at a maximum of 75W so I doubt it would exceed that although that is definitely possible.
    It makes sense though to use an external power supply as it lightens the current that runs through the tiny notebook and it doesn't require a thin and light notebook to come with a big ass 150W Power supply. Split them up serves portability.
  7. Freyqq macrumors 601

    Dec 13, 2004
    not really...thunderbolt is pci-e 4x and desktop video cards require pci-e 16x. Not enough bandwidth to support a decent desktop card
  8. kasbah macrumors newbie

    Aug 11, 2011
    Not true sorry :/

    Its true that TB is PCI x4 but not true that the bandwidth is insufficient... if you compare HD5870 at x4 and x16 the performance hit is somewhere in around the 15% mark @ 1650x1080...

    still worth doing imo
  9. Aldaris macrumors 68000


    Sep 7, 2004
    Salt Lake
    Plus thus is the first generation, thunderbolt has lots of potential on the road map!

    Who knows what we'll have in a few years (like 3-5 years, let's not start the flames that it took nearly 6/9 months for the first peripherals like the promise raid and apple display/hub).
  10. mark28 macrumors 68000

    Jan 29, 2010
    TB = PCI-e cable + minidisplay port interface. That's how it works.

    There obviously is going to be some latency introduced when a GPU is connected threw a cable to the PCI-e slot.
  11. shardey macrumors 6502a


    Jan 28, 2010
    Can you prove that video cards require 16x? I am using a 4870 1gb in my mac pro running 8x and it runnings identically in every benchmark.

    Unless you are running ultra high resolution (5760x1200) then you will NOT see any difference from 8x to 16x. Hell even running in 4x you won't see your computer bottleneck at 2560x1200 resolution

    You should read into some articles before providing misleading information.

    Article 16X vs 8X

    Article 16x vs 4x
  12. Hellhammer Moderator


    Staff Member

    Dec 10, 2008
    Laptops use PCIe too. The difference is that instead of having a physical slot for the GPU (though some laptops use MXM), the GPU (along with other GPU related components such as GDDRs and power switches) is soldered onto the motherboard to save space. The actual connection from the GPU to CPU/PCH (depending on configuration and chipset) is still PCIe though.

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