http://www.macworld.com/article/2065603/imovie-10-0-1-update-supports-older-video-cards.html
http://support.apple.com/kb/HT6023
iMovie (2013): About video card compatibilityInstalling iMovie (2013) previously required a computer with an OpenCL-capable video card. This requirement was removed, and you can install iMovie version 10.0.1 on any Mac with OS X Mavericks.
http://www.macworld.com/article/2060533/imovie-10-review-a-lot-to-like-a-few-quibbles.html
http://www.macworld.com/article/2055452/hands-on-imovie-for-mac-and-ios.html
http://www.macfreak.nl/nieuws/25478/imovie-voor-mac-1001-ondersteunt-meer-videokaarten/