EDD revenue decreased slightly, mostly due to lower Xbox 360 platform revenue, offset in part by Skype and Windows Phone revenue. Xbox 360 platform revenue decreased $418 million or 24%, due mainly to lower volumes of consoles sold and lower video game revenue, offset in part by higher Xbox LIVE revenue. We shipped 1.7 million Xbox 360 consoles during the first quarter of fiscal year 2013, compared with 2.3 million Xbox 360 consoles during the first quarter of fiscal year 2012. Video game revenue decreased primarily due to the release of Gears of War 3 in the first quarter of fiscal year 2012 with no comparable major releases in the first quarter of fiscal year 2013.
EDD operating income decreased, due mainly to higher cost of revenue and research and development expenses. Cost of revenue grew $151 million or 14%, largely due to payments made to Nokia related to joint strategic initiatives and due to the acquisition of Skype, offset in part by decreased sales of Xbox 360 consoles and lower video game royalties. Research and development expenses increased $140 million or 44%, primarily reflecting higher headcount-related expenses related to interactive entertainment and the acquisition of Skype.