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Microsoft's power drain bug patch: Does it work?

By - Source: Tom's Hardware US | B 0 comment



Chicago (IL) and Munich (Germany) -Not quite four weeks ago, Microsoft issued a patch for a serious power drain issue in notebook computers that are running Windows XP SP2. Our engineers took a close look at the patch and its effects to find out whether Microsoft dropped a Q&D fix or if the company in fact resolved a problem that can reduce the battery running time in notebooks by up to 90 minutes.

Previous Power Drain Bug Coverage on TG Daily:
Microsoft driver bug saps Core Duo power
Microsoft to release patch for power drain bug

If you have followed our coverage about the power drain bug, its discovery and impact on notebooks, you may have been as surprised as our engineers that were able to verify its existence back in February of this year. However, it was not just the bug itself that raised eyebrows it was especially the circumstances that surrounded the bug, which accelerates battery power drain as soon as a USB 2.0 device is connected to a Windows XP SP2-based notebook.

Microsoft and its partners had been aware of the bug for almost half a year at the time, but the information about its existence was kept from the public until we unveiled it in our comprehensive coverage. Not the partners are to blame, as they were constrained by a non-disclosure agreement with Microsoft; we are still dazzled that Microsoft kept the issue a secret and did not bother correcting a considerable driver problem in its operating system for quite some time.

But, better late than never and finally, here it is. A patch that promises to fix the power drain bug. Of course, we were interested how well the fix works and took two very different Core Duo notebooks through several test runs, with and without patch.

First up was a 17" multimedia notebook. The Asus A7Jc carries pretty much what system builders can pack these days into a portable form factor. The 10.6-pound computer came with a Core Duo T2400 (1.83 GHz) processor, a 17.1" display, two 100 GB hard drives, 1 GB of memory, as well as a capable mobile graphics chip (256 MB ATI mobility Radeon X1600). There was also a preinstalled and USB 2.0 1.3 megapixel camera in the device that exploits the power drain bug,

We sent the A7Jc through a total of six test runs, examining the impact of the patch on the notebook under varying conditions, with and without a connected external hard drive as well as under maximum and minimum brightness settings.


It was clear from the start that the A7Jc feature set would not allow exceptional battery times, but the running times are sobering for anyone who is considering a multimedia notebook. Under maximum brightness settings, the running time was 105 minutes, which was increased by about 7% with Microsoft's patch (112 minutes). The numbers for minimum brightness were in a similar range of improvement: 117 minutes and 129 minutes, respectively.

We were disappointed by the performance of the patch, as the gain in battery time was almost negligible. But then, we were not able to determine with absolute certainty the impact of the USB 2.0 camera on the system in the first place. Without knowing the loss caused by the camera, our test result only allowed a very speculative conclusion.

We decided to use a very basic Core Duo notebook for a second test. The HP Compaq nx7400 is one of most basic dual-core notebooks you can buy these days. The system is equipped with a Core Duo T2300E (1.66 GHz) processor, 512 MB of memory, a 15.4" display, Intel's GMA950 IGC, and a 60 GB hard drive. In this scenario, the hotfix worked well.

At maximum brightness, the notebook turned in a running time of 184 minutes without patch and without connected USB 2.0 hard drive. We then connected our drive, which caused the battery time to drop by about 16% to 155 minutes. After installing the patch, the running time jumped back up to 185 minutes. We observed a similar scenario with minimum brightness settings. An initial time of 250 minutes decreased by about 20% to 199 minutes when the drive was connected. With installed patch, the nx7400 regained lost battery time and checked in at 248 minutes.

So, apparently Microsoft has taken the problem seriously and fixed the initial driver problem, at least in the case of the nx7400. However, we have our doubts that the patch in fact reclaims all lost battery time in our A7Jc notebook. It's nearly impossible to evaluate the impact of the patch on all available notebook platforms. But in both of our cases the update has a clear positive effect, which is why we recommend Windows XP SP2 notebook users to install the patch provided by Microsoft.

One mystery of the power drain bug remains unresolved, however. Is it a bug that primarily affects Core Duo notebooks or not? After we had published our first article outlining the existence of the bug we got our heads washed by one other website for focusing on Core Duo in our article. Even if we clearly pointed out that other processors may be affected - Intel stated that all mobile CPUs, including the Pentium M and AMD's Sempron and Turion, would give up battery time - the Core Duo always appeared to be the primary target of the bug in any of our benchmarks.

Microsoft somewhat confirmed this observation to TG Daily and mentioned that the power loss caused by a connected USB 2.0 is "much more pronounced" in Intel-based dual-core notebooks than in the previous, single-core product generation. In a statement sent to TG Daily, the company said that "anyone who is using any USB 2.0 devices while on battery on the latest generation of Intel chipsets (Core series) [and] who is experiencing faster than expected battery drain, should install this fix."

We were not able to get more details on what Microsoft means by "much more pronounced," which leaves a question mark behind the overall impact on single-core notebooks. Interestingly, Microsoft never singled out the Core Duo as only affected processor in its original Knowledge Base article and referred to an issue that relates to "Windows XP-based portable computer[s that] may not have as long a battery life under certain circumstances when certain USB 2.0 devices are connected."

You be the judge.

Related content:
Microsoft power drain bug fix may only benefit Core Duo notebooks
Download of power drain bug patch (Microsoft)

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