Compatibility: EGA VGA
Expects: AX    1003H
BL    00H = enable bold backgrounds (16 background colors)
01H = enable blinking foreground (8 background colors)
                                                                  
Returns: (none)
                                                                  
Info: This enables or disables blinking foreground colors in EGA/VGA
text modes.  By default, the BIOS enables blinking foregrounds
(characters blink when bit 7 of the Video Attribute is set).

When foreground blink is disabled (BL=00H), all 16 colors are
available for use as background colors.

Notes: This fn is not available on CGAs  and MDAs .  To use this
attractive and often-seen effect, you must program the CGA Mode
Select Register, manually clearing bit 5.  See CGA I/O Ports.
For instance:
mov ax,40H
mov es,ax
mov dx,es:[063H]  ;get port address of the card
add dx,4
mov al,es:[065H]  ;get current value of Mode Select Register
and al,0dfH       ;mask value by 1101 1111 (to clear bit 5)
out dx,al         ;disable blink (set for bold background)
mov es:[065H],al  ;save the new setting

- -

INT 10H 1003H: Select Foreground Blink or Bold Background