The large SoC looks after a multitude of functions and is of enormous complexity, containing upwards of 20 million transistors including both analog and digital components. This chip contains all of the write-side error-correction coding and channel encoding and the transition-shift precompensation, as well as all of the readback channel including analog filtering, A/D conversion, equalization, timing/gain, detection, and error-correction. The servo controllers which close the loops around the spindle motor and the VCM are also part of this chip. In addition, of course, there are the microprocessors and interfaces that control all the basic functions within the drive including power-up/power-down, command sequencing, translating logical to physical addresses, accounting for environmentals (temperature, shock/vibration) and checking drive-health (signal quality, servo quality, ‘soft’ errors, evidence of disk defects, etc.).