I am using mbpr 13' late 2013 with 8GB ram. Every OS X software is running smooth either with or without the external monitor (DELL U2515H). Things are different when I am using parallel desktops. When I run, for example, the PC excel without the external mon, its smooth. But when I run it with a external monitor, its delay and very slow. Could anyone give me a help? Thanks so much!
