On some of the computers in my company Visual Studio 2013 didn't work at all because the onboard graphics card wasn't good enough. I checked for the requirements and found this:

This isn't so clear, I can't understand why some of the computers worked and others didn't and which onboard cards are supported.
I know that Visual Studio 2013 is implemented using WPF and that WPF is utilizing the GPU to perform better, but didn't find anything in the web to elaborate on it.
I would like to know what are the minimum GPU requirements and the recommended GPU requirements in order to work with Visual Studio 2013.
Will an external graphics card perform better than an onboard card?