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That is most likely the sudden motion sensor that grabs your HDD's actuator arm so that the disk doesn't get gouged. This is what causes the stutter in data read. If you want to turn it off this would solve the problem - if you consider it to be a problem - but if you drop it too fast or tap it too hard you will hurt your disk.

This. The thread is now finished.

You shouldn't drop your laptop anyway.
 
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