Beginning with the AMD Catalyst™ 14.7 graphics driver, AMD redesigned the software functionality of AMD Eyefinity technology with a new framework called “virtual topology” to enable exciting new features like Mixed-Mode Display Groups.
The virtual topology framework delivers these features by reporting a single large monitor to the operating system when the user creates an AMD Eyefinity display group.
The WIN+P hotkey cannot be used to switch display modes in such configurations, as the operating system does not detect multiple independent displays. The AMD Catalyst™ graphics driver continues to offer easy hotkey-based switching between cloned, extended and SLS modes.
Please see these instructions for additional details: Switching between SLS Mode and Extended Desktop Mode