Sample CMOS utils for DOS. They allows to write and read PC CMOS.

cmosr.asm

.MODEL    SMALL
COD	SEGMENT PARA
ASSUME	CS:COD,DS:COD
ORG	100H
START:
	XOR	AX,AX
	MOV	CX,256
	LEA	DI,BUF
	PUSH	CS
	PUSH	CS
	POP	DS
	POP	ES
CMOS1:
	MOV	AL,AH
	OUT	70H,AL
	JMP	$+2
	IN	AL,71H
	STOSB
	INC	AH
	LOOP	CMOS1
	LEA	SI,FNAME
	LEA	DX,BUF
	MOV	CX,256
	XOR	BX,BX
	CALL	SAVE_FILE
	MOV	AX,4C00H
	INT	21H
INCLUDE ..\..\LIBRARY\FILE\SAVEFILE.LIB
FNAME	DB	'CMOS.DAT',0
BUF	DB	64	     DUP	(0)
ENDS
END	START

cmosw.asm

.MODEL    SMALL
COD	SEGMENT PARA
ASSUME	CS:COD,DS:COD
ORG	100H
START:
	PUSH	CS
	PUSH	CS
	POP	DS
	POP	ES
	LEA	SI,FNAME
	LEA	DX,BUF
	MOV	CX,256
	XOR	BX,BX
	CALL	LOAD_FILE
	CALL	SET_CONTROL_SUMM
	CALL	COPY_UP
	XOR	AX,AX
	MOV	CX,256
	LEA	SI,BUF
CMOS1:
	MOV	AL,AH
	OUT	70H,AL
	JMP	$+2
	LODSB
	OUT	71H,AL
	INC	AH
	LOOP	CMOS1
	MOV	AX,4C00H
	INT	21H
SET_CONTROL_SUMM	PROC
	XOR	AX,AX
	MOV	DX,AX
	LEA	SI,BUF+10H
	MOV	CX,1EH
SET_CONTROL_SUMM_1:
	LODSB
	ADD	DX,AX
	LOOP	SET_CONTROL_SUMM_1
	MOV	AX,DX
	XCHG	AL,AH
	MOV	WORD PTR DS:[2EH+BUF],AX
	RET
ENDP
COPY_UP PROC
	LEA  SI,BUF
	LEA  DI,BUF+80H
	MOV  CX,80H
	REP  MOVSB
	RET
ENDP
INCLUDE ..\..\LIBRARY\FILE\LOADFILE.LIB
FNAME	DB	'CMOS.DAT',0
BUF:
ENDS
END	START