One of the Xbox One's most exciting upcoming features is backwards compatibility, which will allow all console owners to play select Xbox 360 games on their current-generation system. But this feature wasn't always a sure thing. Mike Ybarra, Xbox director of program management, says in a new interview that some at Microsoft thought backwards compatibility might never happen due to technical hurdles.

"We knew it would be an enormous engineering challenge, and many people told us it would be impossible," Ybarra said in an interview with Xbox Wire. "However, the team had conviction, and delivered. This is what I love most about Xbox: We're all gamers, and fan feedback fuels our passion."

Microsoft was able to overcome those technical challenges, and the feature--one of the top overall requests--is now in testing for Xbox Preview Program members before its public rollout this fall.

"At a fundamental level, we believe that consumers should be able to play their content on the devices they own," Ybarra said about backwards compatibility.

Xbox One backwards compatibility support was announced in June during Microsoft's E3 briefing. It's not hard to see why Microsoft would push so hard to make the feature a reality. According to Microsoft, backwards compatibility helps sell consoles--and it's already happening.

The Xbox One outsold the PlayStation 4 during the week of E3, something Xbox boss Phil Spencer says was attributable in part to the announcement of backwards compatibility. What's more, the Xbox One is now "building momentum" thanks to backwards compatibility and exclusive games, Microsoft CFO Amy Hood said this week.

In other recent news about Xbox One backwards compatibility, Activision's Call of Duty: Black Ops II has overtaken Rockstar's Red Dead Redemption as the most-requested Xbox 360 game.

For its part, Sony has said it has no plans to offer backwards compatibility for PlayStation 4. Executive Shuhei Yoshida said at E3 about Microsoft's solution, "The technology involved must be very challenging."