What's the point of having two versions of Internet Explorer 11 within Windows 8.1?

It’s a good question, and one that Microsoft executives say they haven’t completely solved. Dean Hachamovich, the corporate vice president in charge of Internet Explorer, said that the browser—which appears on both the desktop and Start screen, but in different forms—is bifurcated to satisfy two different sets of users.

“One IE engine does all this wicked-fast, cool stuff,” Hachamovich said Wednesday during Microsoft’s Build 2013 conference in San Francisco. “Why two? Some people live in the desktop for some activities, and we want to make sure when you’re in Windows you have good experiences,” he said.

“Why two? Some people live in the desktop for some activities, and we want to make sure when you’re in Windows you have good experiences."

Hachamovih said that IE11, the version of IE that ships with Windows 8.1, differs from both competing browsers and earlier IE versions in several key ways.

From a hardware-acceleration standpoint, IE11 is wicked fast because it can shift various workloads, including the JPEG rendering pipeline, to a PC’s graphics card. This reduces the load on a PC's CPU, allowing that chip to process other tasks. Microsoft presented SunSpider benchmarks to support its claim.

The new browser version is also more flexible in how it surfaces web content. Within Windows 7, IE9 bookmarks could be pinned to the taskbar. Within Windows 8, IE10 bookmarks could be pinned to the Start screen. But within IE11, those bookmarks can be pinned to Start and serve as live tiles or widgets, dynamically updating information, Hachamovich said.

Then there's a new, efficient approach to tabbing. Microsoft said 100 tabs can be used by IE11 at once, all without putting an undue strain on battery life. This is because IEthe new browser shifts resources away from older, unused tabs, yet it can bring back these tabs almost instantly. IE11 can also increase performance by prefetching an undisclosed number of links and pre-rendering—essentially preloading—two more links, before the user even clicks on them.

March Hachman Microsoft used the SunSpider benchmark to prove the performance of Internet Explorer 11.

IE11 will also save sites, favorites, and other user data across devices, allowing users to pick up where they left off. One exception, unfortunately, is Reading List, a Windows Instapaper clone that works only on the “immersive” version of IE for the Modern interface, and not on the desktop version.

There’s a good chance that IE11 will be implemented inWindows 8, too, although Hachamovich declined to officially confirm that.

SkyDrive updated for Windows 8, too

Shifting one’s content from place to place (and from device to device) is the mantra of SkyDrive, the cloud storage service that serves as the glue connecting all of Microsoft’s software and services.

In Windows 8, Microsoft released both a Windows 8 SkyDrive app as well as a “sync” app through which users can upload files to SkyDrive via a dedicated folder. With Windows 8.1, the sync and SkyDrive apps have been combined, says Dharmesh Mehta, the general manager in charge of SkyDrive and Outlook.com.

The sync app replicates the files stored on a local machine or machines with the collection of files stored in the cloud. For a desktop PC with a terabyte harddrive and just 100 GB in the cloud, this isn't a problem. But for a typical tablet with 16 or 32 GB of storage, it's physically impossible for 100 Gbytes of cloud files to be copied down to the tablet. That's the problem the latest Windows 8.1 version of SkyDrive was designed to solve.

In the new Windows 8.1 version, SkyDrive will only cache a portion of the file—a thumbnail of an image file, for example, or metadata that tells PowerPoint what presentation the file contains. If necessary, and if the user is connected, SkyDrive will download the total file so that the local application can access it. (Users can also select files to store offline, as before.) The bottom line is that SkyDrive now caches about 1 percent of a user’s data store, dramatically saving local storage.

Mehta wouldn’t say whether the same techniques would be applied to the SkyDrive data available to Windows Phone, but it’s a likely bet.