American Megatrends Super Voyager LPX, User Manual

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Chapter 4 VGA BIOS
136
Super VGA Functions,
Continued
System BIOS Processing
The American Megatrends WinBIOS determines the mode to select by
processing a linked list of extended mode supplemental parameters
tables, while evaluating several factors such as memory size, monitor
type, memory clock, and the chipset. From the top down, WinBIOS
services a mode set request once all factors have been satisfied. A mode
that has multiple horizontal frequencies must be sequentially ordered
from the highest frequency at the top to the lowest on the bottom to make
sure WinBIOS always sets the correct mode for the monitor type.
Modes can be added to WinBIOS by manipulating the structure
described above. WinBIOS always looks for the RAM-defined links first
to satisfy a mode set request. If WinBIOS cannot find a mode based on
the current configuration of the video subsystem, the ROM tables are
scanned.
If new modes are added to WinBIOS by defining them in RAM, a TSR
need only modify the negative offsets described above. If modes are
redefined, special care must be taken. If a TSR modifies a specific mode
frequency that has higher frequencies already defined in ROM, all
frequencies must be redefined in RAM.