After showing the world that a PowerPC G4 processor can fit comfortably into a convection-cooled, 8-inch cube, Apple is reportedly readying another feat of G4 legerdemain: the first line of portable computers to use Motorola's graphics-savvy CPU. Sources said the new professional PowerBook, code-named Mercury, will be both slimmer and lighter than its predecessors, with a larger, wider screen and a slick, new industrial design. The system is currently in preliminary testing at Apple's Cupertino, California, headquarters. The company reportedly hopes to deliver the new model in time for January's Macworld Expo/San Francisco. Mercury prototypes pack a single G4 chip running at between 400 and 500MHz, according to sources, although the PowerBooks may ultimately ship in configurations as fast as 750MHz. That will depend on what speed of G4 chips are available in quantity from Motorola or fellow PowerPC manufacturer IBM. Sources said the new machines will include an active-matrix LCD display measuring more than 15 inches with a wide-screen ratio similar to Apple's current flat-panel Cinema Display monitors. Apple reportedly will clothe the system in a new chassis that is more streamlined than the current generation of G3 PowerBooks. Mercury will reportedly have a single FireWire port, two Universal Serial Bus connections, a modem, an S-video jack, and audio in and out ports. It will also feature built-in support for AirPort, Apple's wireless networking technology, and come with a Type 2 slot for a PC Card. Like current iMacs and the newly unveiled G4 Cube, Mercury will include a slot-loading DVD drive, sources said. The new PowerBook will feature a trackpad akin to the input devices on current PowerBook G3 systems. Sources said the company has not determined whether the trackpad will support Apple's forthcoming handwriting-recognition software, code-named Rosetta Stone. Apple declined to comment on the reports. A year after the Mac maker first unveiled the Power Mac G4 at Seybold Seminars/San Francisco 1999, most of Apple's Mac offerings are still based on the PowerPC G3, which lacks the other chip's Velocity Engine enhancements for graphics-intensive calculations and multimedia tasks. While the Power Mac G4 Cube announced at last week's Macworld Expo/New York will join the G4 club when it ships in August, Apple's iMacs, iBooks and PowerBooks all run G3 processors. Availability of the high-end chips proved to be a stumbling block last fall, when "errata" in early versions of Motorola's processor design prevented Apple from shipping G4 systems at a promised top speed of 500MHz. Supplies picked up early this year, when IBM joined Motorola in turning out 400-, 450- and 500MHz G4 processors for the Mac market. What do you think? Tell the Mailroom. And read what others have said.