INT 10H 1aH: Set or Query Display Combination Code
Compatibility: VGA
Expects: AH 1aH
AL Subfn: 00H= Query current display combination
01H= Select DCC (activate a different display)
BX BL=ID of active display;
BH=ID of inactive display
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Returns: AL 1aH (if this fn is supported)
BL ID of active display
BH ID of inactive display
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Info: This returns or updates the DCC byte at 0040:008a.
When AL=00H, the current DCC code is returned in BX.
When AL=01H, the BIOS examines the DCC table to see if the
specified combination is valid, and then deactivates the video
subsystem identified in BH and activates that in BL.
The following display ID codes are recognized
00H no display (BH=00H if only one display is installed)
01H MDPA on monochrome screen
02H CGA color 07H VGA analog monochrome
04H EGA color 08H VGA analog color
05H EGA monochrome 0bH Model 30 analog monochrome
06H PGC color 0cH Model 30 analog color
Notes: DCC handling is mainly a feature of PS/2 hardware; it was
designed as a means to disable the VGA controller on the PS/2's
motherboard in order to take advantage of future improvements in
video technology.
Not many VGA BIOSes provide full support of display combination
switching, though most support subfn AL=00H to indicate type 08H
in BL.
See Also: INT 10H: Video Services
EGA/VGA Data Areas
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