Munich (Germany) and Westlake Village (CA) - Two weeks ago, TG Daily reported that external USB 2.0 devices may cause certain notebook computers to consume power excessively. In the interest of tracking down the source of the problem, Tom's Hardware Guide worked with engineers from both Intel and Microsoft. Through our extensive collaborative research, we can report that an Advanced Configuration and Power Interface (ACPI) driver in Windows XP Service Pack 2 is the sole cause of the unusually high power drainage observed by all three teams. Today, Microsoft confirmed to TG Daily that it is developing a new patch to fix this particular driver bug, whose nature is somewhat different of those addressed by earlier Microsoft Knowledgebase postings.

"The TG Daily article brought to our attention that our existing workaround is difficult to implement," said Michael Burk, PR manager for Microsoft's client team. "We also learned that we will need to issue a BIOS update in addition to a Registry modification, to make sure that the fix will be stable." While the existing workaround, which we reported on earlier, is somewhat efficient in regaining substantial battery time for notebooks connected to USB 2.0 devices, Burk told us this new patch will go even further to address these new issues.

In the meantime, Microsoft does not recommend that customers install the existing workaround, due to potential instability issues. Instead, Burk told us, the company recommends they wait for the patch as well as a BIOS update, both of which are currently under evaluation in Microsoft's labs.

The power drain bug which Tom's Hardware Guide engineers isolated is different from similar power drain issues whose causes and solutions have been made public by Microsoft since 2004. In the intervening weeks since our original story was published, our teams have been evaluating a non-public preliminary workaround, that Microsoft published internally and among selected partners in July of 2005. Our collaborative tests revealed that the new problem's root cause is not - as we already had indicated in our initial article - Intel's Core Duo platform itself, even though the problem crops up on Core Duo notebook systems. Instead, the root cause is a Microsoft ACPI driver that leaves the asynchronous task scheduler component continuously running.

Although the contents of Microsoft Knowledgebase article KB899179, which listed the company's preliminary workaround, have been published on several Web sites, Burk noted that the article remains confidential, and its publication by outside sources has not been officially authorized. While we question Microsoft's reasons for not having published the KB article until today, we have to respect the company's guidelines.

Industry sources told us that Intel apparently also completed development of its own solution. Intel spokesperson Connie Brown could not confirm the availability of this fix, although she mentioned that Intel has been evaluating possible solutions "for some time."

Background noise

At the conclusion of our initial article, we promised we would find a viable solution to the power drain issue, that regains the battery time that is consumed, whether the final cause turned out to be a driver bug or some undiscovered chipset issue. Our findings jump-started a healthy public discussion, which prompted other publications to follow up. At the same time, they lit a fire under Intel and Microsoft, which fueled our collaborative search for the solution.

Although Microsoft responded to our initial investigation by releasing the preliminary fix it had been working on, we believed that simply publishing our preliminary conclusions and leaving them dangling in the air while we moved on to other matters, would be the same as publishing an incomplete account and expecting that alone to inspire others to find the solution. No amount of numbers, no matter how well researched, would compensate for thousands of users losing battery life.

Despite that dual-core notebooks are still virtually non-existent, at least in retail channels, and even Intel's engineers had to scramble to get their hands on a production ready Napa notebook, both firms were able to replicate our test environment.