EDD revenue increased primarily reflecting higher Xbox 360 platform revenue as well as Skype revenue from the date of acquisition. Xbox 360 platform revenue grew $322 million or 9%, led by increased volumes of Xbox 360 consoles sold and higher Xbox LIVE revenue, offset in part by lower volumes of standalone Kinect sensors sold. We shipped 8.2 million Xbox 360 consoles during the second quarter of fiscal year 2012, compared with 6.3 million Xbox 360 consoles during the second quarter of fiscal year 2011.
EDD operating income decreased reflecting higher operating expenses, offset in part by revenue growth. Cost of revenue grew $461 million or 19% primarily due to higher volumes of Xbox 360 consoles sold, payments made to Nokia related to joint strategic initiatives, Skype cost of revenue, and higher royalty costs resulting from an increase in Xbox LIVE digital marketplace third-party content sold. Research and development expenses increased $101 million or 37%, primarily reflecting higher headcount-related expenses, including Skype headcount. Sales and marketing expenses increased $94 million or 27%, primarily reflecting higher headcount-related expenses, including Skype headcount, and amortization of acquired Skype intangibles.