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 email@example.com 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.