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AH = 12h BL = 10h
Return:
BH = video state 00h color mode in effect (I/O port 3Dxh) 01h mono mode in effect (I/O port 3Bxh) BL = installed memory (00h = 64K, 01h = 128K, 02h = 192K, 03h = 256K) CH = feature connector bits (see #00022) CL = switch settings (see #00023,#00024) AH destroyed (at least by Tseng ET4000 BIOS v8.00n)
Note: One possible check for the presence of an EGA or later display card is to call this function with BH=FFh; if not present, BH will be unchanged on return. Another installation check is used by Athena Digital's HGCIBM, which sets CX to FFFFh on calling and checks whether it has been changed on return
Index:
Installation check;EGABitfields for feature connector bits: Bit(s) Description (Table 00022) 0 FEAT 1 line, state 2 1 FEAT 0 line, state 2 2 FEAT 1 line, state 1 3 FEAT 0 line, state 1 4-7 unused (0)
Bitfields for switch settings: Bit(s) Description (Table 00023) 0 switch 1 OFF 1 switch 2 OFF 2 switch 3 OFF 3 switch 4 OFF 4-7 unused
(Table 00024) Values for switch settings on original EGA/VGA: 00h primary MDA/HGC, secondary EGA+ 40x25 01h-03h primary MDA/HGC, secondary EGA+ 80x25 04h primary CGA 40x25, secondary EGA+ 80x25 mono 05h primary CGA 80x25, secondary EGA+ 80x25 mono 06h primary EGA+ 40x25, secondary MDA/HGC (optional) 07h-09h primary EGA+ 80x25, secondary MDA/HGC (optional) 0Ah primary EGA+ 80x25 mono,secondary CGA 40x25 (optional) 0Bh primary EGA+ 80x25 mono,secondary CGA 80x25 (optional)
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