23 Dec
2006
23 Dec
'06
1:20 p.m.
On 22 Dec 2006 at 22:46, Tony Duell wrote:
Indeed I do.
Now, I said 'wnted sector' above. Sectors
don't really exist at the
hardware level, they're produced by formatting. Each sector has a header,
and one of the values in that header is the sector number. The 'wanted
sector' is the one where the sector number in the header is equal to the
sector number given in the rrad or write command. There is nothing in the
hardware which says that sector numbers have to be contiguous -- you could
have sectors 2, 27, 50, 51, 89, etc on a track.
I assume that you mean consecutive. :)
Requires, no--but if you ever want to do multi-sector transfers,
you'd better have sector numbers that are consecutive--that's how the
controller knows what to look for after it's transferred one sector.
And on systems that support implied seeks you'd better have the physical
and logical cylinder numbers the same for much the same reason.
Some backup-prevention schemes [1] back in the 8-bit days used tricks like
that so the standard copy programs couldn't copy the disk.
[1] THe official name was 'copy protection' of course, but the only
people to be really affected by such schemes were legitimate users who
couldn't keep backups.
-tony