Basically when a track is freshly formatted or written in a professional duplicator, it is written as one long signal.
Individual sectors are written from floppy disk microcontrollers by reading the disk until it encounter the appropriate sector address mark, switches to write mode, writes the body of the sector, and then switches off.
A "gap" follows both the header and the sector body in order to compensate for speed differences that might otherwise cause this process to overwrite the next sector.
A track that has not been "modified" will decode as a nice neat set of data, with "invalid" decoding only occurring as expected on sync bytes.
However the process of switching the write mode on and off while writing an individual sector will leave garbage in the gap areas that will usually decode as "invalid" bytes.
A normal FDC just ignores all that, but the Kryflux uses this to alert you that the disk may have been "modified" by a user.
Keep in mind, however, that disks produced in low-volume numbers may have been produced by a secretary or one of the employee's kids just sitting at a computer using diskcopy. That doesn't make a disk any less "authentic", you just have to judge the condition for yourself.
Comments
Basically when a track is freshly formatted or written in a professional duplicator, it is written as one long signal.
Individual sectors are written from floppy disk microcontrollers by reading the disk until it encounter the appropriate sector address mark, switches to write mode, writes the body of the sector, and then switches off.
A "gap" follows both the header and the sector body in order to compensate for speed differences that might otherwise cause this process to overwrite the next sector.
A track that has not been "modified" will decode as a nice neat set of data, with "invalid" decoding only occurring as expected on sync bytes.
However the process of switching the write mode on and off while writing an individual sector will leave garbage in the gap areas that will usually decode as "invalid" bytes.
A normal FDC just ignores all that, but the Kryflux uses this to alert you that the disk may have been "modified" by a user.
Keep in mind, however, that disks produced in low-volume numbers may have been produced by a secretary or one of the employee's kids just sitting at a computer using diskcopy. That doesn't make a disk any less "authentic", you just have to judge the condition for yourself.