(Telecompaper) Steve Ballmer has stepped down from Microsoft's board of directors six months after Satya Nadella replaced him as CEO. In an open letter to Nadella, Ballmer cites his busy schedule as owner of the Los Angeles Clippers basketball team, civic contributions, teaching and study. He tells his successor, "I have confidence in our approach of mobile-first, cloud-first, and in our primary innovation emphasis on platforms and productivity and the building of capability and services as core business drivers." Ballmer said that for the foreseeable future he expects to continue holding his position of owning more Microsoft shares than anyone other than index funds.