tm@polari.UUCP (Toshi Morita) (04/12/90)
kadicky writes: >Clearly, this is not the most accurate of positionings (if the magnets >do not put out exactly the same amount of power, then the head will be >pulled more to one side then the other...), so you probably wouldn't >want to trust various disk drives to seek properly to this position. >However, since writing doesn't seem to affect data 3/4 of a track away, >it's conceptually possible to format a disk using 3/4 track spacing >(giving 140/3 = 46 tracks == 44K extra). No one that I know of has >ever tried doing this...mostly, I assume, because the 1/4 track position >is not all that accurate... Actually, my brother (Aki Morita) and I have tried patching ProDOS to run three-quarter tracks. It didn't work very well because we seemed to have problems getting quarter-tracking to work well - it's nontrivial to write some routines that will get the #^#*$ head nearly perfectly between two phases. ProDOS would complain a lot (click, click...BRRRRT...) so we abandoned the project. If anyone else wants to try something like this I'd like to offer a suggestion: Don't try to move to the half-track in one continuous motion. If you try to do this the inertia of the head will carry it past the half-track and you will wind up with something like a eighth track or a three-eighth track, depending on whether you're seeking from a higher track or a lower tracks. Move to the closer full-phase, then let the head settle for a bit then go for the half-track Toshi Morita ..!uunet!microsoft!uw-beaver!sumax!polari!tm .