The Fast Forward column in the June 19 Business section incorrectly described a Web browser for Mac OS X called Camino. That program is based on an earlier Internet application, Mozilla, not on Firefox. (Published 7/8/2005)

Two weeks ago, Apple Computer said it would follow the advice of its own ads: "Switch." Starting next year, Apple will build Macintosh computers that run on Intel processors instead of PowerPC chips.

That's an enormous shift for the Cupertino, Calif., computer firm. Since the first Macintosh shipped in 1984, Apple has shunned Intel's processors in favor of chips from Motorola and IBM, to the point of trash-talking the Pentium in its ads.

The way Apple put that history aside to put Intel inside has few precedents in the industry. It's like the Air Force buying Russian MiGs, or Ford bolting a Chevy engine into its next pickup.

But Apple had little choice. PowerPC chips, despite a promising design, haven't kept pace with the expectations of Apple or its users. Two years after chief executive Steve Jobs promised a Power Mac with a three-gigahertz G5 processor within a year, neither that nor a G5 PowerBook are in sight.

Intel's advantage isn't speed per se; although its chips outpace PowerPCs in some tests, both kinds of processor work far faster than most users need. Rather, Intel's edge -- which it didn't even have until two years ago -- is what Jobs called "performance per watt" in his June 6 speech announcing the Intel move at an Apple developers' conference in San Francisco.

Intel's Pentium M chip for laptops -- along with upcoming desktop processors built along similar lines -- runs more efficiently than PowerPCs or other Intel chips.

This technology allows for much better laptop battery life than in current Apple PowerBooks and iBooks. It will also permit fast desktops that need little electricity and don't produce much heat -- both critical in compact machines such as Apple's Mac Mini and iMac.

Having chosen that goal, Apple has picked a fascinating route to it. If it does this job right, it won't just get more efficient processors; Apple and its customers will find themselves with unmatched computing flexibility.

Not only has Apple already rewritten its operating system to run on Intel chips -- it had the foresight to write and test an Intel-compatible version of every Mac OS X release alongside the PowerPC versions it shipped -- it's also preparing software called Rosetta to run most existing Mac software on Intel-based Macs.

And it's providing Mac programmers with a development toolkit, Xcode, to create bilingual, "universal binary" programs that run on either chip without alteration.

That's possible because hardly any programs are written in a processor's own dialect. Almost all are written in one of a few programming languages, then automatically compiled, or translated, into processor-specific binary code using development tools like Xcode.

Five Mac shareware developers -- Thorsten Lemke, author of the GraphicConverter image editor; Andrew Welch, president of Ambrosia Software; Brent Simmons, creator of the Web-newsfeed reader NetNewsWire; Cabel Sasser, co-founder of Panic Software; and Mike Pinkerton, an AOL developer working on a Firefox-based Web browser called Camino -- interviewed by e-mail said making their projects universal releases would be, in Welch's words, "no big deal."

They described it as far easier than such earlier Apple transitions as the upgrade from Mac OS 9 to Mac OS X. At worst, Lemke estimated that he'd need two to three months to revise GraphicConverter; at best, Sasser said he'd needed "about an hour and a half" to make a program Intel-compatible.

Among name-brand Mac developers, such firms as Adobe, Intuit and Microsoft have already said they'll have universal releases of their major programs ready.

Apple says programs written in earlier versions of Xcode will be easiest to revise for Intel, while those written in other toolkits will take more time. Universal releases will need more disk space, but not twice as much -- many program components, such as help files, don't change in this process. With disk space as cheap as it is, that seems a reasonable sacrifice.

For applications that haven't been revised, Rosetta is supposed to bridge the gap, running them at most of their original speed -- albeit in more memory.

Although such emulation software often performs grotesquely more slowly than promised, Mac developers who tried Rosetta -- admittedly, on a prototype Mac with one of the fastest Pentiums around -- said it was invisible in operation, with little or no slowdown for older Mac programs.

Rosetta, however, can't run software written for Mac OS 9 or programs that exploit some higher-end PowerPC features.

Apple says it will ship its first Intel-based Macs in mid 2006, with the transition finished by the end of 2007. It says it will continue to restrict OS X to running only on Macs, although I expect to see hackers figure out ways to install it on generic Intel PCs.

Deciding what Mac, if any, to buy in the meantime will be tricky.

A PowerPC-based Mac will be guaranteed to run any Mac software around, and any differences in performance should be minimal at the start. An Intel-based Mac, by contrast, may balk at some existing Mac programs and will probably be buggier at the start.

But an Intel-inside Mac will bring one huge benefit -- Windows compatibility.

First, Apple suggests you'll be able to install a copy of Windows alongside Mac OS X with moderate effort.

Second, Microsoft's Virtual PC program, which simulates an entire PC inside Mac OS X, should run a lot faster.

Third, a program called Wine ( that Linux users employ to run individual Windows programs -- without needing a copy of Windows at all -- can be revised to run at full speed on an Intel-based Mac.

If Apple and its developers can pull all this off -- an enormous "if" -- the Mac will become the most compatible computer around. And if Apple can keep its lead in hardware design, it will also remain one of the most elegant and stylish (if not the cheapest). Imagine this: In a year or two, the best Windows PC may come from Apple.

Living with technology, or trying to? E-mail Rob Pegoraro at