what do you mean switchable graphics? Like the gpu can be swapped out for another one? or switchable as you can choose to run the integrated 4600 or the amd gpu to save power? Either way according to the Lenovo website the G510 laptops do not come with any other gpu besides the integrated 4600.http://shop.lenovo.com/us/en/laptops/lenovo/g-series/g510/#techspecs
Maybe you are looking at an older model that comes with a second gpu if so maybe provide a link?