Works fine. But you need to be on at least build 1970 of Parallels. (The most current build is 3188...however, some retail stores still have builds earlier than 1970 on their shelves. It is OK to buy on earlier build because you can download an upgraded version online.)
Parallels assigns one of the cores to running the guest operating system. The other core is available to the OSX operating system and anything that is running there. This is important because parallels is reliant on OSX for several functions, including real I/O.