2 May
2002
2 May
'02
6:01 p.m.
On Friday 03 May 2002 00:08, you wrote:
You might be able to even isolate the bad bits in
the bad byte, or take a
vote and use the most reported value to store into the good sector or some
other analysis. At the very least, I would record as much of the bad
sector as I could and write out (in a separate file) the known bad spots
from the disk being read.
You might be able to do some of that with a readtrack ,, hard to say
depends on the controller i guess
The start of a sector is all FF's or rather, stream of 1 bits then FE
(or some other address mark) the controller then knows where it
is in the bytestream.
The problem with lost bits in a sector, is that all after that the controller
no longer knows what position its in .. is the next bit the high bit of the
next byte or the last bit of a current byte ? .. theres no way to tell
is there ? same with a tape, well modern scsi tapes anyway, they
are written in 512 byte blocks and here too, same thing.
So in the floppy case or the hard disk case or the tape case,
the next stream of 1's comes along, then the address mark
and the controler knows where it is again and can read more
stuff, but all after the error in the last block, floppy/disk/tape
ya get nothing but a short read.
Funny, on the 9 track tape you dont confront this issue.
9 track tape is 8 bits + parity right ? so here a bad bit dont
cause you to lose the ability to get the next byte and know
that its a valid byte, a physical superiority it has over the
serial streamers ?.
Or am i assuming too much again.
Raymond