Power Mac G5 not as open to Windows

That's because Virtual PC, the leading emulation program for running Windows on a Mac, doesn't support the G5. Microsoft, which acquired Virtual PC from Connectix in February, said a fix for the problem is not around the corner.

"It will be in the next (full) version of Virtual PC," a Microsoft representative said Wednesday, adding that a new edition of Virtual PC is expected within a year. In addition, the representative said the release is due at about the same time as the launch of Office 11, the next version of Office for the Mac. Earlier this month, Microsoft said it was working on Office 11 but would not comment on when it might be ready.

Although it is not clear how many Mac owners actually run Virtual PC, it has long been used by Apple as part of its case that the Mac can work well in a world dominated by Windows-based PCs. On its current Web page listing of top myths about the Mac, the company notes that 15,000 programs run on the Mac but adds that "if you do encounter that rare program which isn't available for the Mac, you can still run it using Virtual PC." It has also made reference to Virtual PC in its "Switch" advertising campaign, designed to woo Windows users to the Mac.

Microsoft said it learned of the problem with Virtual PC and the G5 when it got its first test machine "a couple months ago." The company, based in Redmond, Wash., said it has no plans to release an interim G5-compatible update to Virtual PC before the next version comes out.

Those who try and run Virtual PC on a G5-based Mac are given an error message that says Virtual PC does not support the G5 chip. They are then directed to Microsoft's Web site for Mac customers.

The reason for the incompatibility, according to Microsoft, is that the current version of Virtual PC for the Mac relies on a feature of the PowerPC G3 and G4 processors called "pseudo little-endian mode," which helps boost performance of a Mac when it is trying to emulate a Pentium chip.

"Because the new G5 processor does not support this feature, large portions of the (Virtual PC) for Mac program must be rewritten and carefully tested to work properly on the G5 CPU (central processing unit)," Microsoft said.

An Apple representative was not immediately available for comment.

Cupertino, Calif.-based Apple has just started shipping the first two versions of the Power Mac G5, which uses a new 64-bit IBM processor. A dual-processor version is still slated to begin shipping later this month. CEO Steve Jobs unveiled the machines at a developer conference in June.

Most Mac programs work without modification on the G5, although to take full advantage of the chip, developers can choose to tweak or recompile their existing software. Adobe Systems has already offered an update to its Photoshop image-editing software, which takes advantage of the 64-bit processor.