How much longer does Apple plan to continue its iPhone exclusivity contract with AT&T? Some say until June, when the device arrives on Verizon’s airwaves. Others say fall.

Not unreasonable predictions given issues with AT&T’s network and the simple fact that adding Verizon (VZ) would more than double the iPhone’s addressable market. But perhaps a bit overeager, particularly in light of Apple COO Tim Cook’s remarks about the carrier during a company earnings call Monday.

Asked about AT&T (T), the bad press its network has been receiving lately and the impact of negative reports on the Apple (AAPL) brand, Cook defended the carrier.

“First of all, AT&T is a great partner,” he said. “We’ve been working with them since well before we announced the first iPhone. And I think it is important to remember they had more mobile broadband usage than any other carrier in the world.”

Emphasizing the large view, Cook continued, “And in the vast majority of locations we think that iPhone customers are having a great experience, from the research that we have done. As you know, AT&T has acknowledged that they are having some issues in a few cities and they have very detailed plans to address these. We have personally reviewed these plans, and we have very high confidence that they will make significant progress toward fixing them.”

Now, Cook’s remarks certainly don’t preclude the possibility that Apple will end its exclusivity arrangement with AT&T. But his eager defense of the carrier suggests there’s at least a chance that his company will renew it.

Of course, Apple did a hell of a job talking up the PowerPC architecture too–right up until it dumped it for Intel’s (INTC) x86 design in 2006.

Owners of any Mac with an Intel processor—about 80% of all Macs in use, including yours—will be able to do simple, direct in-place upgrades to the new Snow Leopard edition of the Mac operating system, due out soon. This method will preserve all programs, files and settings without requiring any of the hard-disk wiping, temporary offloading of files and re-installing of programs that Microsoft is requiring to move to Windows 7 from its most popular current version, Windows XP.

Not only that, but Snow Leopard will cost you and other Leopard users just $29, which is $90 less than the Home Premium version of Windows 7. Apple also is claiming that the upgrade will be up to 45% faster than in the past and that it will actually free up an additional 6 gigabytes of hard disk space.

However, that doesn’t mean there won’t be obstacles or issues for some Mac users. Most important, owners of the other 20% of Macs, those whose models use older PowerPC processors—like the G4 and G5—won’t be able to use Snow Leopard at all. It’s the first Mac OS version that runs only on Intel-based Macs. So, if these folks want Snow Leopard, they’ll have to buy new machines, even though some of them bought their Macs as recently as 2006.

Also, although Intel-based Macs running the older Tiger version of the operating system can be directly and simply upgraded to Snow Leopard, Apple is officially requiring their owners to spend more for it. They have to buy Snow Leopard as part of a $169 boxed set that includes other Apple software they may not want.

Given the manual process of moving from Windows XP to Windows 7, isn’t it likely that there’ll be some third-party utility to handle it?

Yes. Seattle-based Laplink Software has announced that it will issue a new version of its PCmover utility—mainly sold for transferring data to new PCs—that will be able perform automated in-place upgrades to Windows 7 on an existing Windows XP machine, including the preservation of programs. I haven’t tested it yet, and can’t swear that it will work properly. More information is at laplink.com under “Latest News.”

Can you recommend software to remove trial/craplet programs? Something suitable for average users?

The one I have used with success is called “The PC Decrapifier,” which removes unneeded trial programs, add-on programs and advertising come-ons known as “craplets.” The software is free at pcdecrapifier.com. Note that it works only on PCs running Windows XP and Windows Vista. Before you use it, make sure to read the list of exactly what it removes, which is on the Web site.

You can find Mossberg’s Mailbox, and my other columns, online for free at the new All Things Digital Web site, http://walt.allthingsd.com.

A boutique semiconductor design company, P.A. Semi specializes in super-low power PowerPC processors. It boasts a rock-star design team littered with Itanium, Opteron and UltraSparc veterans, led by Dan Dobberpuhl, who was among the lead designers on Digital Equipment’s Alpha and StrongARM chips. And in February of 2007, P.A. Semi uncrated its PWRficient 64-bit multicore processors, 2-gigahertz ARM chips that consume just 5 to 13 watts of power, making them 300% more efficient than any comparable chip.

An impressive chip. Question is, what does Apple want with the impressive little chip shop that made it? Perhaps the same thing it was looking for in 2005 when it first approached the company about a supply deal. That agreement never panned out and Apple subsequently signed up with Intel (INTC) and made transition to X86 chips. The switch has gone well. So well, that it seemed almost a foregone conclusion that Intel’s new line of Atom processors would end up in everything from the next generation iPhone to that mythical iTablet, Apple gaming console and next-gen Newton.

But perhaps that’s not the case. Perhaps Atom’s not quite to Apple’s liking? Perhaps, as word on the street has it, it failed to produce the kind of battery life that Apple wants for its ultra-portable designs. Perhaps Apple just wants its own in-house processor design team, one it could use to push its own technical innovations into the market.

Or perhaps P.A. Semi’s working on a new chip so insanely great that Apple CEO Steve Jobs felt compelled to acquire the company? More to follow when Apple reports earnings later today.

Last week, in a surprise move, Apple gave the iMac a brain transplant. It chose the iMac as the first Macintosh model to be converted to work on the same Intel processors used by makers of Windows PCs, rather than the PowerPC processors from IBM that have powered Macs for many years. This was serious surgery to perform on the company’s star product and launched the planned transition to Intel much sooner than originally expected.

Apple’s new Intel-powered iMac.

Apple says it changed chips because Intel’s latest processors are faster and run cooler, and allow for more flexible and creative computer designs in the future. It says the new iMac is two to three times as fast as the old one, mainly because the Intel Core Duo chip it uses packs in the equivalent of two processors.

But there’s a downside. Nearly all existing third-party software for the Mac, including major programs like Microsoft Office, will have to be rewritten to run on the Intel processor — a process that is under way but will take months to complete. Apple had to build into the new model special, invisible, translator software that allows the older programs to run on the new chip in the meantime. This translator software, however, doesn’t work with every program and can slow down the ones it does work with.

So, how did the brain transplant go? Is the new Intel iMac as good as its predecessor? Does the machine’s raw power offset the translation slowdown?

To find out, we’ve been testing an Intel-based iMac against an iMac G5 only about a month old. The two machines look identical and sport nearly identical features. The major differences are hidden under the hood.

For days, we ran a wide variety of software on the two iMacs, and performed all of the common tasks mainstream consumers do — surfing the Web, emailing, instant messaging, word processing, using spreadsheets, editing photos, playing music, managing personal finances, playing simple games.

Our verdict: The brain transplant was a success. The two machines behaved almost identically in our tests. Compatibility is excellent. The new model easily handled all the major consumer software we threw at it. We never noticed the translator software, called Rosetta, and any slowdowns it imposed were so slight as to be indiscernible.

The new model was actually a little faster at a few of the tasks we tried, but nothing like the two to three times as fast that Apple claims. A mainstream user who didn’t know what was under the hood couldn’t tell the difference between them, even after using them for hours. It appears that the faster chip roughly balances out the translation effect.

So, if the new model works only about as well as the old one, what’s the advantage for consumers? Well, the slight, scattered, speed gains we saw should grow greater over time, as Apple and third-party software makers tweak their applications to take full advantage of the dual-core Intel chip. A year from now, an Intel iMac purchased today will likely be notably faster, if you update your software to newer versions.

But, even now, this is a terrific computer. It’s still the best consumer desktop on the market. It still runs crisply, still is free of viruses and spyware, still has the best operating system and the best built-in software of any desktop we’ve tested. Given how smoothly the new machine works, and how likely it is to get even better, we would prefer it today over the iMac G5, which Apple is still selling for the same price until inventories are gone. The G5 is still a fine machine, but the Intel model has a brighter future, and, based on our tests, it seems ready to go today.

There are a couple of caveats about our results. We tested only common consumer software and tasks, not heavy-duty or professional applications, like Adobe Photoshop, or professional music and video programs, which tend to stress the processor. Some of these nonconsumer products won’t work right until they are rewritten.

Also, there are two drawbacks to the Intel-based iMac that we judged relatively unimportant to most users, but which could be crucial to some. It can’t run old, pre-2001 Mac programs that were written for the old Mac operating system, called “Classic.” And, even though it now uses the same processors that Windows machines do, the new iMac can’t run Virtual PC, the Microsoft program that allows Macs to run Windows software. Microsoft is rewriting Virtual PC for the new Macs but won’t be done until 2007. Some other company may bring out a way to run Windows stuff on the new Mac sooner than that. But, for now, it can’t run Windows programs.

On the other hand, the new iMac has a few advantages. It has a faster video card than the old model and a digital video connector rather than an analog connector.

Doom 3, a non-Apple program, ran well on the new iMac.

From the outside, the two machines are twins. Apple was careful to keep the same physical design, a beautiful white flat-panel monitor with the entire guts of the computer stashed behind the screen in an amazingly thin space. Both have a built-in camera and microphone. The user interface and software features are also identical. Both models run the same excellent Mac OS X operating system. And both also include Front Row, the special interface that allows you to view photos and videos, and play music, from across a room using a small, included remote control.

Even the price of the new model is the same — $1,299 for a version with a 17-inch screen and $1,699 for one with a 20-inch screen.

For our tests, we copied all the third-party software and files from our iMac G5 to the Intel iMac, so the machines were configured comparably. Both had the same amount of memory, the same DVD drives and the same Internet connections.

We ran a mix of Apple and third-party software. We weren’t surprised that all the Apple programs, like iTunes and iPhoto and the Safari Web browser, ran perfectly and swiftly. Apple has already rewritten them for the Intel chip.

But we were pleasantly surprised by the performance of non-Apple programs. We tested Microsoft Office, Adobe Reader, the Firefox Web browser, Skype, Google Earth, Quicken, the Eudora email program, Doom 3, Kodak EasyShare and others — none of which had been rewritten. All launched quickly and ran smoothly and well.

We did find one program that wouldn’t run at all on the Intel iMac: AOL for Mac OSX. But AOL’s main features can all now be accessed from its Web site, so you don’t need this software in most cases.

Web pages loaded swiftly on the new iMac, though not markedly faster than on the old model. We changed the font on a thousand-word document in Microsoft Word and saw no lag at all. We created a chart in Microsoft Excel, and it appeared almost instantly. Email worked indistinguishably well.

This column was written in Word on the Intel iMac, and there were no glitches or hitches or hang-ups of any kind.

On four of our test tasks, the new model outperformed the old one significantly — all in Apple software that had been rewritten for the new chip. It was 15% faster at importing music from a CD, using iTunes. It was 42% faster at converting a video clip from one format to another, using Apple’s QuickTime program. It was 44% faster at importing nine large digital photos into iPhoto. And it was 24% faster at duplicating a huge folder filled with more than 27,000 files occupying more than 12 gigabytes of space.

Why didn’t our results support Apple’s claim of a two to three times speed gain? Like most computer companies, Apple bases such claims on special, complicated benchmark software that doesn’t necessarily match up with the kinds of mainstream consumer tasks we tested.

The bottom line: Apple’s iMac, with its new Intel processor, is still the gold standard of consumer desktop PCs. And it stands to get better over time.

• Email: MossbergSolution@wsj.com.

There’s a reason this was big news in the computer world. For decades, Intel’s chips have been tightly linked to the software of Apple’s archrival, Microsoft, and Apple has touted as superior the IBM PowerPC chips that powered the Mac. Plus, Apple CEO Steve Jobs, probably the most charismatic business leader in America, attracts attention for anything he does, even though his Macintosh has a tiny share of the PC market.

But what does Apple’s move mean for the average consumer, who just wants the best computer for the job?

In the long term, the change will strengthen Apple and the Mac, which is good news for anyone devoted to that platform or considering switching to it. That’s because Intel’s processors and other chips will give Apple more options than IBM’s products could for building Macs that run faster and cooler, and have longer battery life. The first Intel-based Mac is due in spring 2006.

Even consumers who use Microsoft Windows, which runs on the vast majority of computers, will benefit, because the Mac’s impact on the industry is vastly greater than its market share. Apple is the most innovative major computer maker, and the only one largely dedicated to serving consumers instead of large corporate customers. Almost everything it does is later copied by the Windows PC makers, so keeping Apple strong and innovating is good for Windows users, too.

In the short run, however, the chip changeover should make little difference to average consumers. For all but the techiest techies, changing the processor in these machines will be a nonevent, sort of like changing the engine in next year’s Lexus cars. As long as the new engine is at least as fast and smooth as its predecessor, few drivers would notice or care.

What makes a Mac a Mac isn’t the processor under the hood. It’s Apple’s elegant operating system, OS X, which won’t see major changes for 18 months, and the company’s stylish hardware designs, which it will continue to produce. When you peer at the screen of the first Intel-based Mac, it will look just like today’s PowerPC Macs, only it should run faster.

Of course, if Apple fails to execute the switch well or the Intel processors don’t meet expectations, the Mac could be in trouble. And users would lose if too many third-party software developers decline to spend the money and time to convert their products so they run on the Intel chips.

Here are answers to a few common questions I’ve received about the switch.

Should people hold off buying a Mac that uses the IBM PowerPC processor, which Apple will soon abandon, and wait for the new Intel Macs?

No. If you need a new computer and the Mac was the right choice for you last week, it’s still the right choice. Today’s PowerPC Macs are, in my view, the best consumer computers on the market, and Apple plans to roll out additional PowerPC models this year.

Plus, all new software for the Mac will continue to run on PowerPC models for at least a few more years, the likely life of any Mac you buy now. That’s because Apple has created a tool for software developers that easily creates “universal” programs capable of being run on either the PowerPC or Intel models.

Now that Apple will be using the same processor as Dell, H-P and other competitors, will people be able to run the Mac operating system on these non-Apple machines?

Unless some hacker does a masterful job, the answer is no. Apple intends to keep its operating system and hardware tied tightly together. The new Intel-based versions of the Mac’s OS X operating system will be designed so that they cannot run on non-Apple hardware, and Apple has no plans to license OS X to other PC makers.

Will users be able to install and run Microsoft Windows on the new Intel-based Macs?

Apple’s official position is that it won’t block the use of Windows on its new machines. Unofficially, however, the company says people won’t be able to just buy a copy of Windows XP and install it on an Intel-based Mac. That’s because Apple is unlikely to build in all the standard under-the-hood hardware pieces that Windows is designed to mate with. And it won’t supply any special software called “drivers” to help Windows use the unique under-the-hood hardware Apple will use.

However, I expect some third-party company to supply the missing drivers and otherwise make it possible to run Windows on an Intel-based Mac. Microsoft itself might even do this. That would allow Mac users to run Windows programs that lack Mac equivalents at speeds comparable to a Windows computer’s.

Will Mac prices fall due to the switch to Intel?

There’s no way to tell now, but I doubt it. Apple’s lower volumes, higher quality and unusual designs will likely keep it out of the very basement of the market.

Write to Walter S. Mossberg at walt.mossberg@wsj.com