Belluzzo, a former Hewlett-Packard executive, has left the computer company in the midst of a years-long attempt to return to profitability. The company has been cutting thousands of jobs and is changing its future computer line to use Intel chips and the Linux operating system.
Bob Bishop, 56, a Silicon Graphics board member, headed up SGI's marketing organization until 1995. He joined the company in 1986.
Belluzzo resigned to take a position at a company that doesn't compete with SGI, said spokesman John Cristofano, declining to discuss details.
"Having participated in the formation of our new strategy, I am fully committed to the next phase in SGI's transformation that positions the company for sustained growth and profitability," Bishop said in a statement. "I have enormous faith in the talented people, depth of technology, and customer loyalty resident at SGI."
Belluzzo was named CEO in January 1998, taking over from Ed McCracken.
"As an active board member and the person who led our global sales organization until 1995, he is intimately familiar with the company, its customers, its technology, and its people," SGI board member James McDivitt said in a statement. "Bob brings substantial experience to this position, having built and managed several worldwide sales and marketing organizations at SGI, Apollo Computer, and Digital Equipment Corporation during his 35-year career."