Apple Computer Inc. rolled out its fastest-ever desktop computer on Wednesday with processors that run as fast as 2.5 gigahertz, but the company fell short of its earlier goal to offer a 3.0 gigahertz chip-based system by this month. Apple has been counting on its chip supplier, IBM, to shrink the size of components to permit higher speeds for its microprocessors, the brains that run a computer. As more transistors are fit onto smaller circuits, the speed at which a processor can run increases. The PowerPC 970FX processor made by International Business Machines Corp. has components that are as little...