Enable/Disable hardware blinking provided by text mode on CGA/EGA/VGA cards

BLINK.ASM

;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;; blink control ;;;;;
;;;;;  CGA/EGA/VGA  ;;;;;
; by Soha <soha@jin.sh> ;
; with MASM, 2023/12/09 ;
;;;;;;;;;;;;;;;;;;;;;;;;;

.model small

.stack

.data
	no_ansi_prompt	db "no ANSI.SYS or equivalent detected, please load it in CONFIG.SYS", 0dh, 0ah
			db "$"
	help	db "Turn "
		db 1bh, "[30;5;47m", "blinking text mode", 1bh, "[m"  ; 5 for showing result
		db " on/off on CGA/EGA/VGA cards.", 0dh, 0ah
		db "Usage: BLINK.EXE [/]<1|0>", 0dh, 0ah
		db "Author: Soha Jin <soha@jin.sh>", 0dh, 0ah
		db "$"

	log_cga	db "CGA detected, $"
	log_ega	db "EGA/VGA detected, $"
	log_ok	db 1bh, "[1;37;5;41m"  ; 5 for showing result
		db " OK! "
		db 1bh, "[m", 0dh, 0ah
		db "$"

.code
print macro	data
	mov	dx, seg data
	mov	ds, dx
	lea	dx, data
	mov	ah, 09h
	int	21h
endm

commit: ; dl (0 = off, 1 = on)
	mov	ah, 12h
	mov	bl, 10h
	int	10h
	cmp	bl, 4 ; BL is memory size enum, EGA/VGA should < 4
	mov	bl, dl
	ja	commit_cga
	jmp	commit_bios
commit_bios: ; bl (0 = off, 1 = on), for EGA/VGA
	print	log_ega
	mov	ax, 1003h
	xor	bh, bh
	int	10h
	jmp	committed
commit_cga:  ; bl (0 = off, 1 = on), for CGA
	print	log_cga
	mov	ax, 40h  ; BIOS
	mov	es, ax
	mov	dx, es:[63h]  ; 40:0063 is the port address for 6845 chip
	mov	al, es:[65h]  ; 40:0065 is the current value for MSR
	add	dx, 4  ; MSR (Mode Select Register) address
	and	al, 11011111b  ; clr blink bit
	test	bl, bl
	jz	commit_cga_no_set
	or	al, 00100000b  ; set blink bit
commit_cga_no_set:
	out	dx, al
	mov	es:[65h], al
committed:
	print	log_ok
	ret

main proc
	mov	ax, 1a00h  ; for ANSI.SYS
	int	2fh        ; MS-DOS Multiplex Interrupt
	test	al, al
	jz	no_ansi

	xor	bx, bx
	mov	bl, byte ptr ds:[80h]  ; arg length
	test	bl, bl
	jz	usage
	xor	di, di
ckloop:		mov	ch, byte ptr ds:[81h+di]
		cmp	ch, 20h  ; ' '
		je	ckloop_inc
		cmp	ch, 2fh  ; '/'
		je	ckloop_inc
		sub	ch, 30h
		jmp	ckloop_exit
ckloop_inc:	inc	di
		cmp	di, bx
		jb	ckloop
		jmp	usage
ckloop_exit:	mov	dl, ch

	cmp	dl, 1
	ja	usage
	call	commit
	jmp	exit

no_ansi:
	print	no_ansi_prompt
	jmp	exit
usage:	print	help
exit:	mov	ax, 4c00h
	int	21h
main endp
end main

Prebuilt EXE can be found here.

• BLINK 0 disables blinking, can use 16 colors on background in text mode
• BLINK 1 enables blinking, can use 8 colors on background in text mode

Tested with CGA/EGA/VGA cards on 86Box (emulator) with 8088.

Tested with CGA (HD6845) and VGA (Cirrus Logic GD5429) cards on Book8088 (a laptop with 8088 made in 2023).

Tested with VGA (Chips & Technologies F65555) card on Toshiba Satellite Pro 480 CDT (a laptop with Pentium w/ MMX 233MHz).

There are more details in my blog (Chinese only).