Apple Computer Inc. (AAPL) said Tuesday it starts shipping its first portable computers made with Intel Corp. (INTC) chips this week, after announcing last year it would switch from IBM chips.

Apple shares climbed nearly 4 percent to a session high of $67.22 Tuesday, making it the second biggest percentage gainer in the Nasdaq 100 index, as the news appeared to calm investors' worries that Apple's sales might suffer during the shift to Intel chips.

"Their announcement this morning that they have begun shipment of the MacBook Pro [has] alleviated concerns about speculated delays in shipment," said Steve Lidberg, analyst at Pacific Crest Securities. "This is a transitional quarter for them and the market is reacting to that."

Apple announced the switch in processors in June, saying it would move all of its flagship Macintosh computers to Intel processors by the end of 2007.

Apple said it will ship its MacBook Pro notebook with a model at about $2,500, sporting a 2.0 gigahertz Intel Core Duo processor, and a $2,000 model featuring a 1.83 gigahertz processor.

Both models are fitted with faster Intel Core Duo processors than previously announced, but the computers will sell at the same price as previously stated.

"It's good news for our customers," said David Moody, vice president of Mac hardware product marketing," in a telephone interview.

Previously, Apple had planned to ship the MacBook Pro starting at $1,999 with a 1.67 gigahertz Intel microprocessor. The high-end MacBook Pro starting at $2,499 was to ship with a 1.83 gigahertz processor.

Apple stock has slipped some 22 percent over the past month. Apple had been using chips made by International Business Machines Corp. for its Macintosh computers, but its shift to Intel chips caused it to lose some holiday-quarter sales, Apple Chief Financial Officer Peter Oppenheimer said in January.

Apple shares rose $2.28, or 3.5 percent, to $66.99 early Tuesday afternoon. Intel also rose, climbing 19 cents, or 0.9 percent, to $21.32, on Nasdaq.