Apple Computer and IBM Corp. are jointly developing a Macintosh-based "notebook product" that both companies will market, and Apple will cut 50% of its Macintosh models over the next year as part of a plan to simplify product lines and reduce costs, Chairman Gil Amelio said. Speaking at Apple's conference for software developers in San Jose, Calif., on Monday, Mr. Amelio also said Apple will invest in a marketing program to promote MacOS. He said Apple also will spend $20 million to market the Macintosh platform, including new spending on in-store programs. He promised to bring "professional management practices" to fix the troubled company. "This is Apple," he said, "Expect the impossible."