Apple Computer Inc. on Monday introduced the last of its computer models to be converted to Intel chips and said it would launch the next version of its operating system in spring 2007, but some investors expecting a new iPod were disappointed.

Shares in Apple fell 1.6 percent after Chief Executive Steve Jobs did not have his trademark surprise at Apple’s annual software developers conference, such as a new music player or new digital movie rental service.

“They announced exactly what people were expecting. To get a rise (in stock price) you have to surprise investors,” said Gene Munster, an analyst at Piper Jaffray.

The week-long conference has long focused on the Macintosh computer and is aimed at developers who create applications for the Mac beyond what Apple turns out.

Apple announced the new line of high-end desktop computers called the Mac Pro that will use Intel Corp.’s (INTC.O: Quote, Profile, Research) Xeon chipset and run twice as fast as the version it replaces.

The Mac Pro line replaces the Power Mac series and will use dual Xeon chips in each computer. Apple said a computer in the new line with a suggested configuration would retail for about $2,500. The new machines were shipping on Monday.

Apple ended the second quarter with 4.8 percent of the overall U.S. PC market, up from 4.4 percent a year earlier, according to market research firm IDC. Apple’s share of the U.S. retail notebook market doubled to 12 percent as measured by units in June from January.

In Apple’s most recent quarter, better-than-expected sales of Mac and iPods helped fuel a 48 percent rise in net income. Investors took the strong computer sales to mean Apple can look to its Mac platform for future growth and not just to the iPod.