The decades-long partnership between Bill Gates and Steve Ballmer — friends since Harvard, then chief executives who built Microsoft together — cooled after Ballmer stepped down as CEO in 2014. Ballmer later said the two had 'drifted apart,' rooted in a 'fundamental disagreement' over whether Microsoft should build its own hardware and how aggressively to chase the smartphone market. 'Microsoft was kind of the thing that really bound us,' Ballmer reflected; 'since I've gone, we really have drifted a little bit.' Both have said they remain on cordial terms despite the rift.