martin_haye wrote:
On Dec 28, 7:51 pm, Sheldon Simms <wsspa...@gmail.com> wrote:... If that's the case, then the whole idea of "accelerating" the motor is kind of silly even though the code may successfully seek to the correct track.I can add that my own experience developing NakedOS involved empirically determining values that would work, and that I found acceleration to be definitely necessary. If I started out stepping to fast, the stepper wouldn't move at all. There were some mentions in Beneath Apple DOS (I think) about Shugart specs, and I suspect Woz actually had access to technical docs for the stepper and used a table computation to arrive at the acceleration/ deceleration values.
While that may be so, acc/dec head movement was virtually unknown in the floppy world at that time, since seeking was done with very simple "step up/step down" logic. I think that Woz, who was doing all the drive control in software, simply saw an opportunity for speedup and persued it. I'd bet that the values he used were at least partially the result of experiment. The Disk ][ was the fastest-seeking Shugart floppy drive on the market because of his more sophisticated control (not to mention the higher effective data rates from his use of GCR).
I'm fascinated to learn about POKEing new speed values in for newer drives into DOS. That's so cool I have to try it with my IIc.
I suspect you'll find significant seek speedups! -michael NadaNet 3.1 for Apple II parallel computing! Home page: http://home.comcast.net/~mjmahon/ "The wastebasket is our most important design tool--and it's seriously underused."