The Core Duo battery drain saga that was originally reported by Tom’s Hardware has resurfaced. Anand Shimpi later correctly proved that the battery drain bug had absolutely nothing to do with Core Duo, but was actually a problem with Windows XP SP2. Just yesterday, Microsoft got around to publishing a fix for the problem.

The Core Duo battery drain saga that was originally reported by Tom’s Hardware has resurfaced. Anand Shimpi later correctly proved that the battery drain bug had absolutely nothing to do with Core Duo, but was actually a problem with Windows XP SP2. Just yesterday, Microsoft got around to publishing a fix for the problem.

The problem apparently plagues Windows XP notebooks that cannot correctly enter into processor idle sleep states, or C-states. When the processor cannot enter these states, the processor idles, but at a higher state. The result is wasted battery life and a slightly warmer CPU.

There are many reasons why Windows XP SP2 does not let the CPU enter into the correct state, but the one reason seemed to revolve around notebooks that have USB controllers that do not turn off. The original ASUS Core Duo notebook, for example, had an integrated web camera that would leave a USB controller enabled at all times. Microsoft stresses that the patch does not fix notebooks with that particular problem — it only repairs the ACPI driver that governs which C-state the processor should reside.

The patch only exists for x86 versions of Windows XP, Service Pack 2.