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Microsoft driver bug saps Core Duo power

Microsoft driver bug saps Core Duo power
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Munich (Germany) and Westlake Village (CA) - Connect any USB 2.0 device to your notebook and lose more than one hour of battery time: Tom's Hardware Guide's tests of a Windows-based Intel Core Duo mobile processor platform revealed a serious power consumption issue that, according to Intel, is caused by a Microsoft driver bug - a bug that has been known by Microsoft for some time, but kept from the public eye until today.

UPDATE 14 Feb 2006: Microsoft to release patch for power drain bug

In Tom's Hardware Guide's review early last week of a Core Duo-based notebook with Intel's 945 PM chipset and ATI's dedicated X1600 GPU, our test engineers reported stumbling across a mysterious power consumption issue. The unit tested showed abnormally high power consumption, which at first, they believed could be attributable to the Core Duo processor itself, with the high-performance graphics system being an alternate candidate.

But engineers with whom we consulted later in the week indicated that the issue may lie with the chipset of Intel's new dual-core platform, which previously was code-named "Napa." We spoke with representatives of major notebook computer manufacturers, all of whom asked us not to reveal their names, but all of whom said this particular issue has prevented their systems from achieving the goal of four to five hours of battery life which Intel had led them to expect. After a series of extensive tests involving battery benchmarks, Tom's Hardware Guide's Munich Labs engineers were able to observe the precise power consumption problem involving the Core Duo 945 GM chipset.

Our assessment and observations, coupled with extensive consultation with engineers familiar with Intel dual-core architecture, plus information we received today from Microsoft, have led us to conclude that an anomaly in the way the currently available version of the ICH7-M Southbridge communicates with Microsoft's ACPI driver, is at the heart of the power drain issue.

Intel ICH7-M Southbridge

TG Daily and Tom's Hardware Guide have been in communication with Intel representatives throughout this week about our findings described in this article. Late Friday, Microsoft acknowledged to TG Daily - via the hands of Intel - that they believe the problem our engineers observed to have been caused by a misbehaving driver included in Windows XP SP2 - specifically, the Advanced Configuration and Power Interface (ACPI) driver, which is part of the operating system's power management scheme for USB 2.0.

The delicate issue about this bug, provided to Microsoft partners under confidentiality guidelines as Knowledge Base article KB899179, is the fact that it has been known to be a "problem" at least since 12 July 2005. It is unclear at this time why Microsoft has not issued a patch or an advisory the public to fix or explain this bug. So far, Microsoft has not responded to our inquiries and we are still waiting for a comment on this power drain issue.