Even the entry-level model of Apple’s updated desktop is well outfitted. Last month, Apple updated its iMac all-in-one desktop computers, revamping the internal architecture and refining the look of what was an already stylish design. Externally, the biggest change for the iMacs lay in the move to larger 21.5-in. and 27-in. LED-backlit screens and a 16-by-9 aspect ratio. (The earlier 20-in. and 24-in. models had a slightly squarer 16-by-10 ratio.)