T61 Audio

Hello all,

Got a quick question about the T61 audio. Does anyone else experience a problem where the audio skips when you close the lid?

I noticed this when I shut down my computer, and as Windows shuts down, it makes its normal shut down audio sound. Now at the same time, I was closing my lid and noticed that the windows shut down sound skipped.

So I tried it with an MP3 and its the same thing. The audio skips at the point where the monitor turns off. So for some reason, closing the lid makes my audio skip.

Is there a fix for this? Anyone else noticed this problem?

 

This is my uneducated guess

LCD backlights that use CCFLs (just about every one but LED screens) take big amounts of voltage (ive dissected a screen and seen a plethora of caution high voltage transformers on the back), when you are closing your screen the backlight is powering off and it could cause a small voltage/current swing in the batteries/power inputs output and power needed causing the speakers to skip for a moment.

 

that is possible.
could there be any other reason?

more importantly, should this be something I should be concerned about?
The audio doesn't skip unless I open/close the lid and the monitor turns off/on. I'm just concerned that its a hardward issue and that there's a bad connection or wiring and some time down the line, its gonna break.

 

The exact same thing happens to me with an X61s. This has happened to me consistently since I bought it.

To reiterate:
- The problem has been confirmed on a T61 and on a X61s.
- The problem occurs when opening the lid (not when closing it). For me, the problem also happens when applying or removing AC power.
- The problem occurs regardless of the type of media file being played.
- I have found that, when playing a media file with Windows Media Player 11, the effect is that a short piece of the sound being played is repeated (perhaps 500ms). When playing with Winamp, the effect is a short silence (gap) of roughly the same length.

I have a theory, though it's a bit far-fetched. It's based on the observation that the gap always occurs during power management-related activities.

I think the ThinkPad BIOS is using SMM (System Management Mode) to handle power management events (such as opening/closing the lid or changing the AC state). This mode overrides even the lowest-level operating system drivers and takes over control of the CPU. Perhaps the amount of time that the CPU stays in that mode is too long for the audio drivers to refill the hardware audio buffers. Now, since audio hardware can typically be set to, in case of a buffer underflow, to either replay the last sample or play silence, this is why the behaviour is different depending on the application.

The real question is, why does the BIOS PM handler keep the CPU in SMM so long? These handlers are specifically designed to be extremely small in order to not disturb the operation of the OS.

Well, anyway, just a theory. Anyone else have this problem?