Are you talking about a fast render machine or a render drive? Render drives are about 10000 dollars and can be stacked in unlimited amounts. They are faster than almost every computer because they are strictly dedicated to graphics rendering. You can also make a computer to do this and is usually referred to as a render farms. They can be as fast or slowas you want and can do the rendering for you while your other computer does what it wants. My school had 4 of these stacked together and could render very complex animations in minutes. They use physical means to add radisotiy etc.....here's a link to one of them..... http://www.renderdrive.com/