On Mon, 14 Jan 2002, Simon Owen wrote: > [EMAIL PROTECTED] wrote: > > Now I know that BDOS formats & verifies both sides before > > moving to the next track which is handy, but why should there > > be any difference in the physical format - of is it just the > > floppy drive in the PC is a bit too fussy? > > Probably not a perfect test, but I've looked at the source for BDOS 1.5a > and MasterDOS 2.3. The only difference in the physical format seems to > be MasterDOS using an extra three 0x4e bytes (27 compared to 24) at the > end of each sector, which it comments as "more time between sectors". > Might just be the PC being sensitive to that?
I haven't examined the source, but do both formats have the same track skew? I may have got that terminology wrong. What I mean is that IIRC SamDOS aligns sector 1 of track 1 with sector 2 of track 0, and continues to spiral outward. The reason for this is that after reading all the sectors of track 0, you're likely to want to read the first sector of the next track; but by the time the head has moved between tracks, the disk has spun past the point at which sector 1 would have started. By moving the sector along up to the place where the next one would have started, the head gets enough time to move and can start reading sooner, rather than waiting until the disk has gone all the way round again. I don't think MSDOS generally does this, and sometimes I've used Linux PCs which were confused unless the disk was formatted without skew. MasterDOS has a DVAR which allowed you to change the number of sectors to offset by, including zero. Andrew -- --- Andrew Collier ---- ---- http://mnemotech.ucam.org/ --- -- r<2+ T<4* cSEL dMS hEn/CB<BL A4 S+*<++ C$++L/mP W- a-- Vh+seT+ (Cantab) 1.1.4
