When should the SS Mode check box be selected?
This is no description in the Product Guide.
It is only visible in the Vivado 2015.2 DisplayPort v6.0 (Rev. 1) GUI but missing in Vivado 2015.3 DisplayPort v6.1.
This was intended to be a hidden selection for internal use by the DisplayPort IP.
It was removed from the DisplayPort v6.1 GUI in Vivado 2015.3 as it is not intended for customer use.
The user should leave the SS Mode check box unselected.