Compatibility: VGA
Expects: AH    12H
BL    36H
AL    setting: 00H enable refresh
01H disable refresh
                                                                  
Returns: AH    12H if a valid value was passed in AL
                                                                  
Info: This modifies bit 5 of the VGA's Sequencer Clocking Mode Register

You can draw complex graphics faster while refresh is disabled
(it avoids some enforced wait states).  Be sure to re-enable
refresh when finished updating video memory.

See Also: INT 10H 12H (EGA/VGA Special Functions/Alternate Select)
- -

INT 10H 12H BL=36H: Enable/Disable Screen Refresh