With Microsoft set to launch the first beta of a significantly faster Internet Explorer later today, wrangling for pride of place in hardware acceleration is heating up, and getting some rivals hot under the collar.

Internet Explorer 9 will tap Windows Vista and Windows 7 PCs' graphics processors to speed up rendering, assembling and displaying a browser page. Microsoft has touted the technique, called "hardware acceleration," since it announced IE9 almost a year ago, and has been aggressively promoting the technology since last March, when it rolled out the first preview.

Microsoft beat on the acceleration drum even harder last week, when Ted Johnson, the program manager lead responsible for the browser's graphics and rendering, boasted that IE9 is the only browser to use what he called "full hardware acceleration."

In a long post to the IE blog last Friday, Johnson argued that only IE9 calls on the graphics processing unit (GPU) for all three major phases of creating a page: rendering the content, assembling the page, or "compositing," and displaying it on the desktop.

Every other browser adding hardware acceleration, Johnson implied, was a half-baked effort.

"Based on their blog posts, the hardware-accelerated implementations of other browsers generally accelerate [rendering or compositing] but not yet both," Johnson said. "Today, IE9 is the first and only browser to deliver full hardware acceleration of all HTML5 content."

That raised hackles at Mozilla, the open-source developer of Firefox.

"Microsoft is wrong; we accelerate content and compositing," said Mike Shaver, Mozilla's head of engineering, just hours after Johnson's posting.

Mozilla technology evangelist Asa Dotzler was more blunt. "The facts are that Firefox takes advantage of the same Windows 7 APIs that Microsoft does to accelerate both the compositing and the rendering of Web content," Dotzler said in Friday post to his personal blog. "Mozilla provided test builds of Firefox ... with this hardware acceleration well before Microsoft did. We are faster and we were first."

Two days later, Robert O'Callahan, a Mozilla developer who works on the browser's graphics infrastructure, chimed in. " 'Full hardware acceleration' is a bogus phrase," O'Callahan maintained. "All browsers pick and choose how to use the GPU, and more use of the GPU isn't necessarily better."

Like IE9, Firefox will rely on hardware acceleration to increase performance on Windows Vista and Windows 7 by using the Windows Direct2D and Direct3D APIs for content rendering and compositing. Mozilla switched on Firefox's content acceleration in the latest Windows beta of Firefox 4 last week.

But Firefox will also have something Microsoft won't: support for the aging but still widely used Windows XP.

Microsoft has said that IE9 won't run on XP, with hardware acceleration cited as one of the reasons. Last year, Microsoft made the decision not to add support for Windows 7's Direct2D API to Windows XP, as it did for Vista. When Microsoft releases the IE9 beta later today, Windows XP users need not apply.

That got Mozilla crowing.

"Firefox accelerates for Windows XP users too, something Microsoft says they can't do," said Dotzler last week. "If Mozilla can accelerate browsing for the hundreds of millions of PC users on Microsoft's Windows XP, why can't Microsoft?"

According to the most recent statistics from Web metrics company Net Applications, two out of every three computers running Windows is running XP.