John Mallard, CEO of PortalPlayer, has resigned. No reason has been given.

He helped launch PortalPlayer, which is the company that produces the processor at the heart of Apple's iPod, in May 1999. CNet reports the CEO resigned last week, but remains involved in the company in a consultative role. The company's chief operating officer RS Turnbull has also switched to a consultancy role, the report claims.

The company provides the technology for hard drive-based portable-music players and home-stereo systems. The company's involvement with iPod has never been formally announced. More companies are expected to introduce devices based on the company's technologies in January, the report claims.