Epson 486SX - Manual (Page 145)

The formatting options work as follows:
Format first scans the disk for defective (bad) tracks and
lets you decide which tracks to mark as bad. Then it
formats the disk and marks the bad tracks so they are never
used to store data.
Destructive surface analysis tests the entire disk
for read/write errors or unflagged bad tracks and updates
the defective track table. Because this option writes and
reads data on the disk, it destroys all data on any track that
produces an error. You cannot run the Destructive surface
analysis on a disk that has never been formatted.
Non-destructive surface analysis checks the disk
for unflagged bad tracks without destroying data. You
cannot run the Non-destructive surface analysis on a disk that
has never been formatted.
The type of format you choose depends on whether you are
reformatting a disk that has been used or formatting a new disk
for the first time. See the recommendations below.
Formatting a New Disk
Many hard disk drives come with a printed list of bad tracks
but the bad tracks are not flagged on the disk. You may need to
modify the defective track table to add the bad tracks. Other
hard disks (such as those supplied by Epson) come with the
bad tracks already flagged. If you are formatting a new hard
disk that has never been formatted, select the Format option.
Physically Formatting a Hard Disk A-3