Not content with making bold claims about the performance and efficiency of future iterations of its Atom processor line, Intel used its investor relations day to point out just how much better Windows would be on Intel than on ARM.

Intel Senior Vice President Renée James said that Windows on ARM would offer no backwards compatibility at all with existing x86. Instead, James said that Windows on ARM processors would exclusively offer a new, mobile-oriented, touch-friendly interface. In contrast, x86 versions would include both the new interface and a "legacy" interface suitable for conventional laptops and desktops. x86 systems would, therefore, offer the best of both worlds: a new interface for new tablet form factors, and a conventional interface for the enormous body of existing x86 Windows software. The chance of ARM ever running such software? In James' words, "Not now. Not ever."

Intel CEO Paul Otellini also sought to downplay the Windows on ARM port. He described it as not one but in fact four separate ports, to four separate ARM system-on-chip designs—NVIDIA, Qualcomm, Texas Instruments, as previously announced by Microsoft, and one other. Such a comment was plainly intended to portray ARM as a complex platform on which incompatibility is rife—in contrast to x86 Windows, where users can more or less run any application from the past 20 years without having to give compatibility a second thought.

The claim that Windows on ARM would not support legacy x86 programs is not extraordinary. In fact, Microsoft itself has made similar comments: when the ARM port was announced at CES earlier this year, the company said that support for x86 programs was not likely. But the suggestion that ARM Windows would not offer any kind of compatibility with existing Windows software was more than a little surprising—not least because Microsoft has already shown off a recompiled version of Office running on ARM, and promised that Office on ARM would be available to buy.

Strong denials

Redmond seems more than a little displeased at the comments made by Otellini and James. An unusually strongly-worded statement issued by the company reads:

Intel's statements during yesterday's Intel Investor Meeting about Microsoft's plans for the next version of Windows were factually inaccurate and unfortunately misleading. From the first demonstrations of Windows on SoC, we have been clear about our goals and have emphasized that we are at the technology demonstration stage. As such, we have no further details or information at this time.

Of course, the statement does not say which of Intel's claims were wrong, though the compatibility issue seems the most likely candidate; if ever there were a legacy application, it's Office, and so if Office can be recompiled for ARM, it's likely that other "legacy" software can similarly be recompiled. Support for "legacy" Office in turn suggests that Windows on ARM will include support for traditional software, and won't be restricted to the new, mobile-oriented interface that is likely to be a key feature of Windows 8.

The "four ports" statement may also be misleading—Windows already has to gloss over certain minor hardware variations that exist between the different hardware platforms it supports, but nobody would argue that support for both Intel and AMD processors, not to mention the many chipsets available for each vendor's processors, requires multiple ports. The differences between ARM SoCs may be a little greater than those on the x86 side, but surely not enough to justify Otellini's statement.

Intel missing the point

But even if everything Intel said was spot on, so what? Having four ARM ports may incur an incremental cost for Microsoft, but it's highly unlikely to make a difference to anyone else, as underlying variations are sure to be abstracted away and hidden from software developers. Even if the four ports materialize as four separate versions—Windows for Tegra, Windows for Snapdragon, Windows for OMAP, Windows for mystery fourth architecture (a Microsoft-designed ARM chip? The company has a license to produce such a thing, and might want to use a custom processor in the next generation Xbox)—such differences will only matter to OEMs, who will have to ensure they pick the Windows version that corresponds to the SoC they've chosen. This is at worst a minor bit of trivia for nerds to obsess over.

The relevance of having four ports may be slim to none, but at least it's a real issue to manage, at least for Microsoft and perhaps the OEMs. The comments about legacy software, however, are pure denialism. The reason that Microsoft is porting Windows to ARM is not because the company has ambitions to support an ARM-based ecosystem as extensive and as varied as the x86 ecosystem. We're not going to see retail availability of standalone ARM processors and motherboards, and we're not going to see companies shipping ARM desktops assembled from off-the-shelf components.

The point of the ARM port is slimline devices with battery life of ten or more hours. That means iPad competitors. Longer term, perhaps in the Windows 9 timeframe, it might also include smartphones. Some of these devices may have optional mice and keyboards—perhaps even Atrix-style docks—and a few might even be convertible laptops of the kind we've seen for many years, but their standard input will be touch screens. These systems will indeed use a new user interface—plenty of leaked information says that Intel was right on that point—one designed for imprecise fingers and on-screen keyboards.

Who needs x86 anyway?

And that new user interface is what makes "legacy software" an irrelevance. To fit into that new user interface—and to work well with touch screens—software will need to be modified. Software that's been cleanly written, with a user interface that's not entangled with the core application code, may be easy to modify. Many applications will need to be extensively reworked. But the need for some alteration is a constant: legacy Windows applications just aren't built for tablet form factors.

Windows on ARM may not be able to run existing, unmodified x86 software. "Not now. Not ever." But people buying Windows-powered ARM tablets by and large won't care, because they wouldn't want to run such software anyway. They'll want to run software that's actually been designed for touch-screen tablets. Some of that software may be all-new; some of it may be derived from existing applications—but in both cases, it will have undergone significant development work to adapt to the new input mechanism. And against that backdrop, the extra work required to port to ARM is negligble. In many cases there may well be no extra work at all; just the selection of a different option when compiling.

It's not surprising that Intel doesn't want to acknowledge this in public. It's not surprising that Intel won't admit that the ability to run existing x86 software unmodified is an irrelevance to a machine that is primarily or entirely touch-driven. Without that legacy software lock-in, buyers no longer need plump for an x86-compatible system at all. Internally, Intel must know all this—it's just not wise to publicly admit that the company's core technology isn't actually very useful.

Microsoft faces the same challenge, of course. That legacy software isn't just x86 software—it's also Windows software. And if applications have to be substantially altered to handle a touch interface, well, perhaps they should just be rewritten entirely to work on an iPad instead. That concern is perhaps the strongest argument for why Microsoft would retain a legacy interface in Windows on ARM, to ensure that access to legacy Windows software would be just a recompile away, even if it means connecting a mouse and a keyboard to use it.