2 May
1999
2 May
'99
10:46 a.m.
On Sun, 2 May 1999, Tony Duell wrote:
Which is, of course, a major cause of problems in reading a 360k disk that
has been over written as a 360k but in a 1.2mb drive.
- don
demagnetized.
At the time it was explained that the erase heads write a
narrower path than the read heads scan so if the track has been magnetized
on the outside it can interfere with the reading and writing of a block.
On all drives, the erase head is _wider_ than the R/W head. That's a
simplification, as actually the R/W head erases the middle of the track,
but what matters is that the drive erases a wider track than it reads or
writes.
It has to. However carefully you make and align a drive there will be
_some_ positioning errors. And if you write a narrow track than you read,
you'll end up _always_ reading a mixture of what you've just written and
what was there before.
-tony