MSDOS 6.2 Master Boot Record

7C00 START                 CLI                                        
7C01                       XOR     AX,AX           ; AX=0000
7C03                       MOV     SS,AX           ; SS=0000
7C05                       MOV     SP,7C00         ; SP=7C00 (start)
7C08                       MOV     SI,SP           ; SI=7C00 (start)
7C0A                       PUSH    AX                                 
7C0B                       POP     ES              ; ES=0000
7C0C                       PUSH    AX                                 
7C0D                       POP     DS              ; DS=0000
7C0E                       STI                     ; Disable interrupts
7C0F                       CLD                     ; Set direction flag=inc.
7C10                       MOV     DI,0600                            
7C13                       MOV     CX,0100                            
7C16                       REPNZ                                      
7C17                       MOVSW                   ; Relocate the MBR from
                                                   ; 7C00 to 0600.  Copy the
                                                   ; first 256 bytes of the
                                                   ; MBR.  This copies a few
                                                   ; extra bytes at the end
                                                   ; just in case.  The boot
                                                   ; sector will be later
                                                   ; loaded at location 7C00.
7C18                       JMP     0000:061D       ; Basically jumping to
                                                   ; 7C1D at new loc. 061D.
7C1D                       MOV     SI,07BE                            
7C20                       MOV     BL,04                              
7C22                       CMP     BYTE PTR [SI],80                   
7C25                       JZ      7C35                               
7C27                       CMP     BYTE PTR [SI],00                   
7C2A                       JNZ     7C48                               
7C2C                       ADD     SI,+10                             
7C2F                       DEC     BL                                 
7C31                       JNZ     7C22                               
7C33                       INT     18                                 
7C35                       MOV     DX,[SI]                            
7C37                       MOV     CX,[SI+02]                         
7C3A                       MOV     BP,SI                              
7C3C                       ADD     SI,+10                             
7C3F                       DEC     BL                                 
7C41                       JZ      7C5D                               
7C43                       CMP     BYTE PTR [SI],00                   
7C46                       JZ      7C3C                               
7C48                       MOV     SI,068B                            
7C4B                       LODSB                                      
7C4C                       CMP     AL,00                              
7C4E                       JZ      7C5B                               
7C50                       PUSH    SI                                 
7C51                       MOV     BX,0007                            
7C54                       MOV     AH,0E                              
7C56                       INT     10                                 
7C58                       POP     SI                                 
7C59                       JMP     7C4B                               
7C5B                       JMP     7C5B                               
7C5D                       MOV     DI,0005                            
7C60                       MOV     BX,7C00                            
7C63                       MOV     AX,0201                            
7C66                       PUSH    DI                                 
7C67                       INT     13                                 
7C69                       POP     DI                                 
7C6A                       JNB     7C78                               
7C6C                       XOR     AX,AX                              
7C6E                       INT     13                                 
7C70                       DEC     DI                                 
7C71                       JNZ     7C60                               
7C73                       MOV     SI,06A3                            
7C76                       JMP     7C4B                               
7C78                       MOV     SI,06C2                            
7C7B                       MOV     DI,7DFE                            
7C7E                       CMP     WORD PTR [DI],AA55                 
7C82                       JNZ     7C4B                               
7C84                       MOV     SI,BP                              
7C86                       JMP     0000:7C00                          

7C8B                       DB      'Invalid partition table',0
7CA3                       DB      'Error loading operating system',0
7CC2                       DB      'Missing operating system',0