File:Mac Pro 2012 vs 2013 expansion.jpg

Comparison of internal vs. external expansion options between the 2012 and 2013 Mac Pro models. The German text translates to:
 * with:


 * 4 hard drives
 * DVD burner
 * Blu-ray drive
 * Audio interface
 * Video capture interface
 * Fiber channel interface

Source

 * The Sad Truth About Expansion On The New Mac Pro by Buster Hein, Cult of Mac. 2013-07-10.