EDD revenue increased primarily reflecting higher Xbox 360 platform revenue. Xbox 360 platform revenue grew $409 million or 33%, primarily reflecting increased volumes of Xbox 360 consoles sold and higher Xbox 360 video game revenue led by Halo Reach. We shipped 2.8 million Xbox 360 consoles during the first quarter of fiscal year 2011, compared with 2.1 million Xbox 360 consoles during the first quarter of fiscal year 2010. Halo Reach launched in September 2010 generating approximately $350 million of revenue during the quarter.
EDD operating income increased primarily reflecting revenue growth, offset in part by higher operating expenses. Cost of revenue increased $152 million or 19% primarily due to higher volumes of Xbox 360 consoles sold. Research and development expenses increased $65 million or 30%, primarily reflecting higher headcount-related expenses. Sales and marketing expenses increased $39 million or 27% due mainly to increased Xbox 360 platform marketing activities.