Specifications

AMD Geode™ GeodeROM Functional Specification 185
Video BIOS Support
32087C
13.1.19 Function 12h: Alternate Select Functions
Operates the interface to a variety of miscellaneous functions.
13.1.19.1 Subfunction 10h: Return Video Information
Returns additional information about the adapter mode that is not available in Function 0Fh. This function was intro-
duced with the EGA, and was a common method of detecting an EGA in the system. For compatibility reasons, all
VGAs return a memory size of 256 KB in this function no matter how much more memory may be installed. Also, since
very few VGAs have dip switches, the value returned in CX is meaningless and is actually an emulated EGA switch set-
ting value.
Passed:
Returns:
13.1.19.2 Subfunction 20h: Alternate Print Screen
Replaces the print screen handler at INT 05h with one that recognizes more than 25 rows. The original PC/AT mother-
board BIOS assumed all modes use 25 rows, something that can not be assumed with EGA or VGA adapters.
Passed:
Returns:
None.
Parameter Description
AH 12h
BL 10h
Parameter Description
BH Color flag:
0 = Color mode
1 = Mono mode
BL Memory:
0 = 64 KB
1 = 128 KB
2 = 192 KB
3 = 256 KB
CH Feature Bits
CL Switch settings
Parameter Description
AH 12h
BL 20h