Sunday, December 7, 2008
Lenovo T500 noise issue
So as many others have reported with other laptops, the Lenovo T500 makes a high-frequency whining noise. After going through at least 6 cases with Lenovo tech-support (they had no idea what to make of it and kept thinking it was the fan), including replacing the fan, it got escalated, and tech support returned the laptop with 'CPU power management' disabled in BIOS. Investigating further, and it looks like alternating the CPU to low power states C4 onwards causes it to make the noise. Thinkwiki has a bunch of suggestions on reducing the noise, but the only one that reliably worked is to prevent the CPU from entering those states. I found this is done either by the BIOS setting change, or I found that plugging in a USB mouse also prevented the CPU from entering the power saving state - as reported by powertop. I'm running Ubuntu on it. I've heard elsewhere people had tricks on windows to tell the OS how to schedule the power cycling, but I haven't tried them.