On Mar 26, 16:16, Richard Erlacher wrote:
> I'm not sure I am the one who should wake up here. I would repeat "It
> doesn't matter whether the diskette is a 1.2 MB one or a 360K type" but
it
> does depend what sort of drive it is.
No, Fred is right. There are plenty of drives designed to use single
density or double density disks at 96 tpi, and disks cerified for such use,
and they work perfectly reliably for 80 tracks, SD or DD. Historically,
such drives predate 1.2M (HD) drives. Provided you use SD/DD media in a
drive using the correct write current, and providing there isn't any other
leftover rubbish for the wider heads in a 48 tpi drive, any reasonably
well-aligned 48 tpi will handle those disks just fine. However, no 48 tpi
drive I have ever heard of is designed to use HD 1.2M media, and if you try
it, it will give trouble sooner or later. All the evidence indicates that
the major factor is the magnetic coercivity of the media.
> [...] the fact that the heads designed for 48tpi will write a
> significantly wider swath on
> the diskette than the 96tpi drive can erase. Consequently, and I'll bet
> you've had this experience, you can format a bulk erased diskette to
48tpi
> with a 96 TPI drive and have it work for a while.
>
> The more the diskette is written, by the 48tpi drive, the harder it
becomes
> for the 96tpi drive to erase its writing,
Again, no. Providing you're only reading back the part overwritten by the
96 tpi drive, this is not true. It only matters if you both write with 48
tpi, overwrite with 96 tpi, and then try to read back with a 48 tpi drive
-- which is not what was being discussed. And it doesn't make any
difference whether the 48 tpi drive writes once or one thousand times, the
magnetic field strength is the same!
> and, of course, the 48TPI drive
> will have the most trouble because the signal not erased in the 96tpi
drive
> is perceived by the 48tpi drive as noise, while the signal written by the
> 96tpi is written at a lower level to begin with, since the drive relies
on
> the higher coercivity of the medium to generate a larger signal amplitude
if
> that factor is to come into play at all.
No, it doesn't rely on the higher coercivity, not when it's writing single
or double density. It only does that for High Density.
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
Received on Sun Mar 26 2000 - 19:10:23 BST