PUSH AX
PUSH DX
PUSHF
PUSH DS
MOV DX, 1BC9h
MOV DS, DX
MOV AX, [3000h]
INC AX
MOV [3000h], AX
MOV DX, 378h
OUT DX, AL
POP DS
POPF
POP DX
POP AX
JMP 04B2:1875

MOV AH, 25h
MOV AL, 08h
MOV DX, 1BC9
MOV DS, DX
MOV DX, 8000
INT 21h