Refer to the map here:
http://www.streetdirectory.com.sg/mapsize2.jsp?x=21745.299&y=31120.158&level=7&star=1&oldX=21035.64&postal=117576&oldY=31214.42&heading=NATIONAL+UNIVERSITY+OF+SINGAPORE+%28NUS%29%3CBR%3E1+ENGINEERING+DRIVE+2%2C+SINGAPORE+117576

Strange enough, they are not reflected in either this online map or NUS's own residences for students list.