[Coco] 80 track disk access under RSDOS
flexser at fiu.edu
Wed May 5 12:29:56 EDT 2004
On Wed, 5 May 2004, (John Kowalski) wrote:
> At 03:38 AM 05/05/2004 -0400, Art Flexser wrote:
> >On Tue, 4 May 2004, (John Kowalski) wrote:
> >> >From what I recall, RSDOS assigns granules in a particular order on blank
> >> disks - starting from track 18, going up to the max, then starting again at
> >> track 0 and going up to track 16. (Track 17 is the directory track).
> >My recollection, possibly faulty, is that RSDOS starts at a track in the
> >middle of the range, as you say, and then assigns granules working outward
> >in BOTH directions.
> I was only going from memory as well, so either one of us might remember the
> details better.
> The reason I recall the way I described is because it seems that it would
> cause less unnecessary track skipping when loading files longer than 1 granule.
> If a file were to be split up across multiple tracks, at least the tracks
> would still be adjecent/in sequential order.
> Actually, maybe the second half I described (where it fills tracks 0-16
> last) might go in 16-0 order instead - where it starts near the directory
> track, then works it's way to track zero. We'd be both mostly right that
> way :)
> John Kowalski (Sock Master)
On the other hand, working outward from the center in both directions
would minimize overall head movement since everything, including the
directory track, would be located as close to the center of the disk as
possible. Maybe it is only when assigning the first gran of a file to be
saved that it works that way, so that skipping around within a particular
file would also be minimal. Now that I think about it, I think that
scheme jibes with my recollection.
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