[coreboot] Investigating the high pitched noise on the x60 tablet

Peter Stuge peter at stuge.se
Mon Jun 9 23:56:19 CEST 2014

Charles Devereaux wrote:
> I would like to investigate the whining noise issue.
> I have a spare motherboard that I'm setting up for studying this noise
> issue by pinpointing from which component it comes from
> by default going into a power saving mode that make this noise.

The noise is not created by a particular state.

The noise is created by switching between states.

I expect that the noise comes from power supply circuitry.

Use an oscilloscope in clever ways to find the source.

idle=halt skips all C-states.

uhci_hcd requires the CPU to run every ms.

Factory BIOS and coreboot have different noise.

Thermal shutdown is fairly easy to induce when running coreboot,
but not with factory BIOS. X60 has notoriously poor thermal design,
but still there is no thermal shutdown with factory BIOS. Find why.

Understanding the thermal issue might be helpful for the noise issue.

Learn how the factory BIOS manages the CPU power states.

You will not be able to find the documentation you may want for this.


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