File:Backside Mac Pro vs Power Mac G5.jpeg

Summary
Backside of a Power Mac G5 (left) and a Mac Pro (right)

Source

 * File:Backside Mac Pro vs Power Mac G5.jpeg by Kyro, Wikimedia Commons. 2009-02-24.
 * a tale of two Macs by Blake Patterson, Flickr. 2006-08-18.