Int 10H [MCGA] [VGA] Function 12H (18) Subfunction 33H (51) Enable/disable gray-scale summing

Enables or disables gray-scale summing for the currently active display.

Call with:

AH = 12H

AL = 00H to enable gray-scale summing

01H to disable gray-scale summing

BL = 33H

Returns:

If function supported

AL = 12H

Note:

When enabled, gray-scale summing occurs during display mode selection, palette programming, and color register loading.