It's not SLI. By default it's probably set to use Optimus where it's using the integrated Intel video as the main GPU, and then running things that need more performance on the GT 750.
Normally that'll work fine, but if you run into some compatibility issue, I think you can disable Optimus on that system. (By the way, being able to disable Optimus on a notebook is SUPER rare...the Alienware ones are the only ones I know of that can actually.)
I *think* that on the newer systems you can disable it by (inside Windows) pressing FN + F5, then rebooting, and it'll switch over to just using the GT 750 and disabling the Intel GPU.
I've got a M17x-R4, and in my case it's FN + F7, I think, but I think on the newer systems it's F5.
Someone please correct me if I'm wrong! Not sure whether you can disable Optimus on that new Alienware 13 or not...I guess it must be using Optimus to copy the output from the video card you have in that external enclosure back to the internal screen?
SLI is a technology that combines multiple GeForce GTX GPUs through an SLI bridge.
Switchable Graphics is the technology that allows to manually switch between the integrated and the discrete graphics card using the FN+F7 or FN+F5 command.
NVIDIA Optimus Technology combines the integrated Intel graphic card with the discrete NVIDIA GPU while running graphic-intensive applications. Both the Alienware 14 and the Alienware 13 are setup by default to run on the integrated Intel graphics and only switch to the NVIDIA GPU for preset applications. In these models, there's no function key to switch manually between the two cards.
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