Specifications

192 AMD Geode™ GeodeROM Functional Specification
Video BIOS Support
32087C
13.2 VESA BIOS Extended Functions
This subsection is based on the VESA BIOS Extensions (VBE) Specification Version 2.0. Applications use VBEs to get
information about a video controller and then setup an environment in which the application program can work. For exam-
ple, an application may call Function 00h to get a list of modes that “may” be supported and then call Function 01h to see if
the mode is supported and to get information about that mode, such as video memory address. The application would then
call Function 02h to set the video mode. When writing to display memory, it may be necessary to “bank” the correct memory
aperture at the video memory address. This is handled by Function 05h.
VBE functions exist as Function 4Fh in addition to the INT 10h vector standard VGA BIOS function. The VBE function code
is placed in the AL register and 4Fh is placed in the AH register. Any additional registers used are dependent on the VBE
function. If the VBE function exists, AL is set to 4Fh on return. The completion code is returned in the AH register, see Table
13-3. Table 13-4 listed the supported VBE functions.
Table 13-3. VBE Completion Codes
Return Value Description
AL = 4Fh Function is supported
AL != 4Fh Function is not supported
AH = 00h Function call successful
AH = 01h Function call failed
AH = 02h Software supports this function, but hardware does not
AH = 03h Function not available in current video mode
Table 13-4. Supported VBE Functions
Function Subfunction Page Number
Function 00h: Return VBE Controller Information 194
Function 01h: Return VBE Mode Information 194
Function 02h: Set VBE Mode 194
Function 03h: Get VBE Mode 194
Function 04h: VBE Save/Restore State 195
Subfunction 00h: Return Buffer Size in BX 195
Subfunction 01h: Save State 195
Subfunction 02h: Restore State 196
Function 05h: VBE Set/Get Bank 196
Subfunction 00h: Set Bank 196
Subfunction 01h: Get Bank 197
Function 06h: VBE Set/Get Logical Scan Line Length 197
Subfunction 00h: Set Scan Line Length in Pixels 197
Subfunction 01h: Get Scan Line Length 197
Subfunction 02h: Set Scan Line Length in Bytes 198
Subfunction 03h: Get Maximum Scan Line Length 198
Function 07h: VBE Set/Get Display Start 199
Subfunction 00h: Set Display Start 199
Subfunction 01h: Get Display Start 199
Subfunction 80h: Set Display Start during Vertical Retrace 199