Apple Desktop 21.5 inches

Display
21.5-inch (diagonal) LED-backlit display with IPS technology 1920-by-1080 resolution with support for millions of colors

Processor

2.7GHz 2.7GHz quad-core Intel Core i5 processor (Turbo Boost up to 3.2GHz) with 6MB L3 cache
2.9GHz 2.9GHz quad-core Intel Core i5 processor (Turbo Boost up to 3.6GHz) with 6MB L3 cache
Configurable to 3.1GHz quad-core Intel Core i7 (Turbo Boost up to 3.9GHz).

Memory

8GB (two 4GB) of 1600MHz DDR3 memory
Configurable to 16GB.
Storage
2.7GHz
1TB (5400-rpm) hard drive
2.9GHz
1TB (5400-rpm) hard drive
Configurable to 1TB Fusion Drive.

Graphics

2.7GHz
NVIDIA GeForce GT 640M graphics processor with 512MB of GDDR5 memory
2.9GHz
NVIDIA GeForce GT 650M graphics processor with 512MB of GDDR5 memory
Video Support and Camera
FaceTime HD camera
Simultaneously supports full native resolution on the built-in display and up to a 30-inch display (2560 by 1600 pixels) on an external display
Support for extended desktop and video mirroring modes

Audio

Stereo speakers
Dual microphones
Headphone port
Headphone/optical digital audio output (minijack)
Support for Apple iPhone headset with microphone