Windows and Intel Macs: What you need to know

Apple's announcement of new Macs based on processors from Intel raises an interesting question: Since both the Mac and Windows operating systems now run on Intel-based hardware, shouldn't it be easy to run both on the same computer?

That simple question deserves a simple answer. But there isn't one — at least not right now. Reaching the nirvana of running the two most popular desktop operating systems on one machine is a lot harder than you might expect.

Apple has said that it wasn't planning to support Windows on the its new machines, but the company also said it wouldn't try to stop people from doing so. Still, some of the technical choices Apple has made in designing the new Intel-based Macs have made running Windows a challenge.

The good news? Plenty of people have been working to break down the barriers, so it should only be a matter of time before Windows shows up on the iMac's 20-inch widescreen display.

Even after solving the technical challenges, there are also legal hurdles. Just because you might get Windows running on a Mac, or Tiger running on their Dell, doesn't mean it's legal.

Finally, even if the legal and technical obstacles are overcome, many people say just being able to boot both operating systems independently is not the answer. Most people will want the systems to interact, which means some form of emulation or virtualisation. Some small developers are making promises in this area, but just how quickly this will happen — or how quickly the emulated OS will run — remains to be seen.

We're not engineers or lawyers, but here's our best stab at answering some common questions:

So if the Mac runs on Intel chips and Windows runs on Intel processors, what's the holdup?
The challenge comes in the technical means by which the operating systems load. Windows loads itself using something known as the BIOS. Apple's Intel Macs, however, use a newer technology known as Extensible Firmware Interface.

"These different firmware environments will separate OS X and Windows environments almost as effectively as instruction set architecture did when Macintosh software ran only on PowerPC chips," chip analyst Nathan Brookwood said in an email.

But not everyone is convinced the obstacles are so insurmountable. Envisioneering analyst Peter Glaskowsky noted that Gateway had a Windows Media Centre PC back in 2003 that used EFI rather than BIOS. Gateway, Glaskowsky said, had to change the boot loader that manages how operating systems load.

"It's just not a big deal," Glaskowsky told ZDNet UK sister site CNET News.com. "At some point, I expect it would be in the next week or two, somebody will figure out how to change boot loader on those Macs so that it is smart enough to do the same thing."

In any case, word is that the next version of Windows, called Vista, will support EFI. Some people claim to have made some progress in loading test versions of Vista onto an Intel Mac, though the work is not yet complete.

OK, that sounds complicated. So what about running Linux on an Intel-based Mac?
Discussions about the idea quickly cropped up on a mailing list for Red Hat's Fedora version of Linux. The verdict: Again, it's a matter of writing the right code, but it's not simple.

The challenge here is not the chip, but the way that the operating systems boot. Most Linux versions use a boot loader called GRUB that doesn't support EFI at present, though Itanium versions of the operating system use a different one called Elilo that does.

What about going in the other direction: How about running the Mac OS on other Intel machines, like a standard PC?
Apple has said that it will take steps to prevent this from happening. "We will not allow running Mac OS X on anything other than an Apple Mac," senior vice-president Phil Schiller said in a June interview. The company has not gone into specifics, but appears to be using a TPM (trusted protection module) chip as part of its authentication mechanism.

OK, how about programs like Virtual PC, then, that run under the Mac OS but allow Windows emulation?
Microsoft, which now owns Virtual PC, has been a bit cagey on when, or even if, it will bring out Virtual PC for the Intel Mac. The company's public statement is that it sees a need for such software, but hasn't decided whether it will do it. However, the Wall Street Journal's  Walt Mossberg said Microsoft is doing a version and will have it ready next year.

Other emulation makers have been more direct. One small company, iEmulator, has promised that it will have an Intel-native version of its software by the end of February. "We're already in early testing," said general manager John Czlonka. "The performance increase is staggering."

Technical issues aside, is it legal to run Windows on a Mac?
It seems so, but only by purchasing a full copy of the OS, not the upgrade versions typically bought by consumers. Microsoft says that a fully licensed copy of Windows XP Professional can be properly licensed if run on an Intel Mac.

What about running the Mac OS on a non-Apple PC?
There isn't a legal way to do that, given that Apple doesn't sell standalone versions of its operating system. Because all Macs come with some form of the Mac OS, the retail boxes that Apple sells are only licenses to upgrade from one version to another.

CNET News.com's Stephen Shankland contributed to this report.