IIRC my A3k just has jumpers on the drives.
I have HD drives at both DF0 and DF1, both are
reconzied as HD drives. (OS 3.9)
The A2k has a jumper on the MoBo to tell it there
is a DF1 on-board but I don't think there is any
jumper to tell it its a HD drive.
IIRC OS 3.1 on my A3k would only reconize one HD drive.
I had 2 HD drives in it then and only one would be
reconized at a time. If I had a HD disk in one drive
then the other would only see DD disks. But it didn't
seem to matter which drive on the A3k.
I didn't think it would matter on the A2k where the
drive is at, it does see it as a HD drive in the DF0
position.