Existing hardware wasn’t built to rigorous Microsoft standards for the new operating system.

If you’ve been less than impressed with the performance of the touch interface for Windows 8 Consumer Preview it may be because the hardware running it wasn’t designed for the new operating system, Microsoft says.

The eight screen-touch interactions defined for Windows 8 call for screens whose sensitivity may vary from what Microsoft requires of manufacturers who are building machines for Windows 8 specifically, according to the Building Windows 8 blog.

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“[W]hile we ensure that the OS works well with a Windows 7 PC, a new Windows 8 PC is going to be much more consistent and predictable both from a user and developer perspective,” say the authors of the blog, Jerry Koh, a group program manager, and Jeff Piira, a test manager of the Windows human interaction platform team.

When the software is finalized and installed on devices that were designed specifically to support it the experience should be better, they say, and that is the top priority. In the meantime Microsoft has tried to make Windows 8 compatible with machines designed for Windows 7. “So you should feel confidence in installing the Consumer Preview on the machines that you own today,” they write. “However, as much as we value compatibility, we also have to balance this with making Windows 8 really shine on new Windows 8 PCs.”

As an example, they point to the edge-swipe feature that reveals application bars from the bottom of the screen and the charm bar from the right side. “Traditionally, the edges of the screen are where touch sensitivity drops off, and it’s a place that hardware manufacturers have traditionally not placed much emphasis on,” they write. So on Windows 8 machines, those edges will be made more responsive without sacrificing space that the application can use when the bars are hidden.

Since Windows 7 machines had different design requirements, Microsoft had to do a workaround for screens that are not ideal. “In order to make edge swipe work consistently on Windows 7 PCs, we created a mode where there is a 20-pixel buffer to catch the edge swipe gesture. This allows a majority of PCs to reliably invoke the charms and use Windows 8 effectively,” the blog says.

As it says, this may work on a majority of machines, but not flawlessly. On a brand new HP TouchSmart 520 PC tested by Network World, the preview edition sometimes responds the first time with a finger swipe from the left to open up the charm bar, but sometimes it takes two or three swipes. Sometimes it misinterprets the edge swipe for a slide-to-pan swipe which scrolls the screen side to side. So a swipe meant to summon charms can scroll the live-tile screen for the Windows Store, for example.

But Microsoft says it has straightened this out with hardware developers. “There were many challenges here,” the blog says, “but we were able to deliver on the promise of Windows 8 PCs that have the ability to trigger the edge swipe without taking any pixels from applications, and with extremely good edge sensitivity using touch — a promise that benefits developers and users alike.”

Other issues the blog acknowledges:

= Taps don’t always work, especially when typing. This may be due to touch screen response rate and the number of touch points. Or it may be that the user is typing too fast, leaving more than two fingers on the screen at the same time.

= Trouble detecting swipe-to-select motions. This could be because some systems ignore the first few values of a touch, throwing off its interpretation of a swipe.

= Swipe-and-slide can be interpreted as a tap. Again, if the first values are ignored, the swipe is misinterpreted. Slower swiping and sliding can help.

= Swipe from edge doesn’t always work. Similar causes to the previous two issues and the same solution: slower swiping.

In its Windows on Arm (WOA) devices, in which the hardware is wed to the software with tight restrictions, Microsoft is shooting for responsive touchscreens that will inevitably be compared to the performance of iPads, since many WOA devices will be tablets.

The bloggers list some of the machines on which Microsoft has been testing Windows 8: HP Elitebook 2760p convertible; ASUS EP121 tablet; Dell Inspiron Duo convertible; Lenovo x220t convertible; 3M M2256PW 22″ display; Samsung Series 7 slate.

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