Windows 8 on ARM Won't Run Legacy Windows Apps

 By Mark Hachman September 16, 2011 01:34pm EST0 Comments

Microsoft executives said this week that Windows 8 tablets using an ARM chip will not be able to run legacy Windows 7 applications, with the possible exception of Office.

This week, Microsoft held an analyst meeting in conjunction with BUILD, its developer conference in Anaheim, where the company talked more about Windows 8 and provided the first code to developers.

At that conference, however, Microsoft executives said they had made it "very clear" that Windows 7 legacy applications would not run on Windows 8-based ARM tablets - a fact that arguably hasn't been made clear at all.

"I think I said that if it runs on a Windows 7 PC, it'll run on Windows 8," Steven Sinofsky, the president of Microsoft's Windows, said, according to the transcript. "So, all the Windows 7 PCs are X86 or 64-bit.

"We've been very clear since the very first CES demos and forward that the ARM product won't run any X86 applications," Sinofsky said. "We've done a bunch of work to enable that -- enable a great experience there, particularly around devices and device drivers. We built a great deal of what we call class drivers, with the ability to run all sorts of printers and peripherals out of the box with the ARM version.

"What we talked about yesterday was -- what we announced yesterday for the first time was that when you write a Metro style application, all the tools are there to enable you in any of the languages that we support to automatically support ARM or X86," Sinofsky added. "I think that's the key part of everything that we'll run."

Microsoft would normally have two choices for porting the legacy apps over to the new ARM architecture: hardware-based emulation, with some logic for interpreting X86 instructions, or software-based emulation, something similar to the code-morphing software used by the early Transmeta chips. In either case, the performance of the legacy applications would be lower than apps that were natively compiled.

But Microsoft also appears to have passed over the opportunity to clarify the situation. An official Q&A from CES neglected to clarify the issue, for example, and reports from the time did not clarify the issue. Microsoft also addressed Intel chief executive Paul Otellini's comments about "four ports" of Windows 8 on ARM, without specifying its own plans.

Sinofsky claimed that the decision to not include support for legacy software dealt on Windows 8 on ARM lay with battery life and security. Legacy apps weren't written to be "really great in the face of limited battery constraints," a hallmark of the "Metro" tablet interface for Windows 8. Moreover, he added, there would be the risk that malware writers would port viruses over to the Windows 8-on-ARM platform, too.

Microsoft previously demonstrated Microsoft Office running on the new Windows 8 platform, and chief executive Steve Ballmer indicated that that was still a direction for the company.

"When we have something that we want to talk about, we will, but certainly you ought to expect that we are rethinking and working hard on what it would mean to do Office Metro style," Ballmer said.

How should developers think of building apps for the Windows 8 Metro interface? Microsoft addressed the topic in dedicated developer session that PCMag attended. "The main concepts are: using a Metro-style design; creating "fast and fluid" applications; snapping and scaling applications; using contracts for making applications work together; investing in a great "tile"; creating "active" applications, specifically Live Tile; connecting to the cloud; and embracing the basic Windows.

"A Metro-style app is not just a Win32 app that you recompile," said Jensen Harris, director of program management for the Windows User Experience. In general, most Metro applications will be smaller in scope than the monolithic applications that dominate the desktop today, he said.

For more from Mark, follow him on Twitter @MarkHachman.


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