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Can anyone explain me why the 13h interrupt needs a sector-number less than 13?
For example:

Code: Select all

mov ah, 0x02          
mov al, 0x08          
mov ch, 0x00           
mov cl, 0x12            ; Sector 12
mov dh, 0x00             
mov dl, 0x00
int 0x13

That code works but

Code: Select all

mov ah, 0x02          
mov al, 0x08          
mov ch, 0x00           
mov cl, 0x13            ; Sector 13
mov dh, 0x00             
mov dl, 0x00
int 0x13

causes an error (drive not ready)