Abstract: Method and apparatus for determining a signal-to-noise ratio (SNR) value from a readback signal, such as in a data storage device. A readback signal is obtained by a receiver (such as a data transducing head) coupled to a data recovery channel having a variable gain amplifier (VGA) and a threshold detector (TD). The data channel applies a selectable VGA gain value to the readback signal while errors are accumulated using a selectable error detection threshold from the TD. The SNR value is determined at least from a magnitude of the error detection threshold, and preferably from first and second VGA gain values using a linear regression model. The determined SNR value is highly correlated to classical SNR values obtained using external equipment such as an analyzer or oscilloscope, and is advantageously used in automated fashion during high volume manufacturing certification testing.

Abstract: A reader-to-writer offset for a head positioned over a track on a disc in a disc drive having a plurality of tracks is generated by using two iterations. A first iteration is used to determine a fine-tuning range that is used for a second iteration. The first iteration uses coarse steps of the reader across the track pitch to roughly determine OTC boundaries (which are used as the fine-tuning range). The fine-tuning range is determined by locating the point before the first valid reading (e.g., a VGA reading or BER reading with a rate that is less than the BER threshold) and by locating the point after the last valid reading. The second iteration uses fine steps of the reader across the track pitch to determine the actual OTC boundaries. The OTC boundaries are the first valid reading and the last valid reading that are made using the fine steps.

Abstract: A reader-to-writer offset for a head positioned over a track on a disc in a disc drive having a plurality of tracks is generated by using two iterations. A first iteration is used to determine a fine-tuning range that is used for a second iteration. The first iteration uses coarse steps of the reader across the track pitch to roughly determine OTC boundaries (which are used as the fine-tuning range). The fine-tuning range is determined by locating the point before the first valid reading (e.g., a VGA reading or BER reading with a rate that is less than the BER threshold) and by locating the point after the last valid reading. The second iteration uses fine steps of the reader across the track pitch to determine the actual OTC boundaries. The OTC boundaries are the first valid reading and the last valid reading that are made using the fine steps.

Abstract: A data storage device has a plurality of head/surface combinations with different data track densities on at least two surfaces. A minimum head quality is established for the data storage apparatus. Head quality is identified for each of the heads at each of a plurality of track densities. A tuned track density is selected for each surface based on the track density that corresponds to a head quality.