cdaf@iuvax.UUCP (Charles Daffinger) (08/12/86)
In article <3222@utcsri.UUCP> greg@utcsri.UUCP (Gregory Smith) writes: >In article <943@rti-sel.UUCP> jb@rti-sel.UUCP (Jeff Bartlett) writes: >>> ... ? ( Not to mention trimming everything from the drive, e.g door switch, >>> index hole sensor, track zero sensor. TUKATUKATUKATUKATUKATUKA!!) >>> >>> Greg Smith University of Toronto UUCP: ..utzoo!utcsri!greg >> >What bothers me is that even the Apple //c goes 'TUKATUKATUKATUKA' when >aligning its head. If the processor sent 'step in' and 'step out' >pulses to the hardware, it would be a simple matter to add a track-0 >sensor and disable the step-out signal when it sensed track-0. It seems (?) >that the CPU directly controls the stepper-motor coil signals though, so >this annoying noise cannot be easily eliminated without modifying the CPU's >view of the controller, which would break software that bypasses DOS and >would thus be Impossible. I believe Apple would have loved to eliminate >this if it were possible to do it at reasonable cost. > >-- >"You'll need more than a Tylenol if you don't tell me where my father is!" > - The Ice Pirates >---------------------------------------------------------------------- >Greg Smith University of Toronto UUCP: ..utzoo!utcsri!greg Looking inside DOS you will find that any time (a) the arm is being pulled back to track zero (eg, in an init or during boot), and (b) whenever the track found is different from the track expected, RWTS will instruct the stepper moter to move the write arm over $80 phases to make absulutely sure that it is at track zero. (A little rash?) This has been kept around up to the 3.3 controller card and DOS 3.3 (which is just now no longer being supported by Apple). I beleive that PRODOS now only attempts to find the correct track if a seek brought it to a wrong track, rather than attempt to recallibrate the arm. -CDAFfy