On Sun, 29 Apr 2012, Michael J. Mahon wrote:
Enough time passes during the retries that you can do various "stunts" with the drive to vary the instantaneous rotational speed--by lifting it up and rotating it back and forth in a plane parallel to the table-- which is sometimes just what is needed to get a good read! ;-)
I had variable success with slightly opening and closing the door latch, too. That, of course, when totally in despair.
The really sad thing is that the single byte XOR checksum of the sector data is simply not enough. When there is a source of noise (including unreliable data and/or reading process) it is so easy to get "good" sector which is actually garbage, that it's not even funny.