eGPU – Connecting an external video card to a notebook (DIY implementation)

With everything connected, time to see if it works. Having the eGPU powered on, I can finally boot into Windows and we run into this issue when opening the Device Manager.


Basically it tells us that the BIOS/Windows was not able to properly allocate/accomodate the video card memory constraints into the PCI space. So at this point we need a solution to make it fit, and for this we are going to use Setup 1.x, a donationware pack of applications created by nando4 user from the techinferno forums.

After configuring the Setup 1.x and creating a compact batch file in order to rearange devices into the PCI space memory blocks and some tweakings like reboots and disabling video cards in device manager we can finally see both card active in Windows and working perfectly.

Taking a look at devices sorted by connection, we can see the Nividia GTX 680 card connected to the end of a PCI bridges tree on the Southbridge chip, which limits the connections to PCI 2.0 link connections.


Comparing to the Nvidia 765m dGPU connected directly to the Northbridge (PCI 3.0 link connections) we can easily guess those underlying PCI bridge ports could be a source of latency bottlenecking the performance of the external connected card.


GPU-Z tool has a function to report the link speed, as can be seen it the image, the eGPU is limited to a PCI Express x4@2.0 connection. Cuda-Z also is capable to provide some insights on the limitations of memory bandwitth.

Running Furmark on the eGPU we can take a look at the average power consumption.


7 comments la: eGPU – Connecting an external video card to a notebook (DIY implementation)

    1. So you left out the most important information, the penalty of thunderbolt/usb3 and the memory buffering. The most important reasons you see few/no such implementations in the wild.

    2. Compared to desktop, yes. Compared to the dGPU in the laptop…you can see the graphs…

    3. Awesome stuff Monstru! Like it 🙂 Now I want to attach this to my MacBook Pro Retina and do some 3k gaming on it 😀

    4. Glad you like it, I hope it helps a lot of users 😀

    5. Great work!!! Would it be possible to run the pcie with a powered riser? The Sonnet Board needs still be powered, right? Possible to power it through PSU? Thanks

    6. Joseph wrote on:

      I don’t know whether or not I should be posting this here, but I’m having a problem with an egpu unit, when ever I attatch it to my laptop and boot up (either with or without the drivers) my laptop screen on boot up goes to a GPU fail screen (multicoloured and pixelated). I’ve yet to find anyone else with the same problem and from my testing I’ve yet to find a solution :'( .

      If anybody could help me solve this problem I would be over the moon 🙂

    7. What a great explanation. Thanks! From the moment I saw the bandwidth of thunderbolt I knew this would be possible and I am sure there is a commercial market for it. Meanwhile, hopefully more and more enclosures come out with boards which can help make this easier still.

      …and sure, it won’t beat a desktop with the same GPU, but it gives you the chance to have an ultra portable with desktop class graphics which is also upgradable! Brilliant!


    Leave a Reply