Or is it that people don't know what
"DAM" stands for?
MOST don't know what it stands for, [...]
For what it may be worth, I saw "DAM" and wondered what it meant. If I
"Data Address Mark"
<oversimplified>
By writing a byte with invalid clock bits, the controller can create a
byte on the track that is easily recognizable as NOT being part of the
data, regardless of where and when on the track the controller starts
reading.
Such "marks" are used to identify the start of the track (Index Address
Mark) as well as start of data and sector headers.
In addition to the "normal" DAM ('FB'), most controllers are capable of
producing some alternate address marks, in order to maintain maximum
level of incompatability. For example, Superbrain uses 'FA' address
marks.
TRS-DOS uses different address marks for DIRectory sectors V
normal data sectors. When RS went to double density, the DD FDC was
incapable of creating the specific address marks that Model I TRS-DOS
expecte!d BTW, it is rumored that the specific choices made for TRS-DOS
DAMs were due to a misprint of a preliminary spec sheet for the FDC.
