RL drives (was: cctalk digest, Vol 1 #319 - 51 msgs)

On Saturday, December 14, 2002, Johnny Billquist wrote: That shows that the servo bursts are logically associated with a sector, but it does not say that they are recorded at the same radius as the sector data itself. Since the servo bursts are not field-recordable and are not a need-to-know topic (other than the fact that they exist) for the manual you quoted, it is conceivable that DEC simplified (or obfuscated) the fact that S1 and S2 occur at different radii. And having the radially offset servo signals makes more sense to me, anyway. IANAEE, but it seems that with the burts in the track, the drive electronics wouldn't know whether to move the heads in or out; it would only know that it was off-center. With radially (and angularly!) offset bursts as in Tony's diagram, the drive electronics know which burst (inside or outside) the head is closest to, and it would thus be able to discern which direction to move the heads. -- Jeffrey Sharp