Specifications

AMD Geode™ GeodeROM Functional Specification 165
Video BIOS Support
32087C
13.1 INT 10h Functions Descriptions
This section lists those INT 10h functions supported in GeodeROM, the parameters that system software supplies to each
INT10h function, and the values that each function returns.
13.1.1 Function 00h - Set Video Mode
Description:
Sets the VGA into one of several enumerated modes. A “normal” mode set includes clearing the display memory; how-
ever, by setting bit 7 of AL to a “1” allows the mode set to occur without clearing video memory. Note that even if bit 7 is
set, a font still gets loaded in text modes.
On a mode set, these events occur:
1) As determined by the parameter table, all VGA registers are placed into a known state.
2) The cursor position changes to 0, 0.
3) The BIOS variables for mode number, number of rows and columns, CRTC address, etc. are updated.
4) The screen is cleared (if bit 7 of AL = 0 on entry to this function).
5) The RAMDAC is loaded based on mode type.
6) In text modes, the appropriate size font is loaded.
7) Alternate palettes and alternate fonts may be loaded based on the save pointer table.
The font size used in the text mode is based on the number of scan lines on the display. The BIOS saves the last set-
ting of Function 12h, Subfunction 30h (Select Scan Lines) for this purpose. The fonts used in each text mode are
shown in Table 13-2.
Passed:
Returns:
None.
Table 13-2. Text Mode Fonts
Mode/Scan Lines 200 350 400
0/1 8x8 8x14 9x16
2/3 8x8 8x14 9x16
7 N/A 9x14 9x16
Parameter Description
AH 00h = Function number
AL Mode number
DS Seg0