A disk drive is disclosed comprising a disk having a host addressable area and a reserved area, an exception table stored in the reserved area, a head actuated radially over the disk to write data to the disk, and control circuitry coupled to the head. The interpoles couple the first and second magnetic fields to produce a gearing between the first and second gear members. A valid mark bit of a next entry and the valid mark bit in the entry previously processed are read. The receiver can use a moving average of Doppler frequency estimates or a weighted combination of Doppler frequency estimates from different paths of a received signal to calculate the Doppler frequency estimate. Preferably, the dosage is provided by a bilayer tablet. When submersed in liquid, the simultaneous expansion and contraction of the volume in the trucks generates positive and negative buoyancy, respectively, enhancing the dynamics of the truck expansioncontraction motion and the reverse scissorable arm actuation.