Chapter 8 BIOS ROM
8.5.1 SYSTEM ID AND ROM TYPE
Applications can use the INT 15, AX=E800h BIOS function to identify the type of system. This
function will return the system ID in the BX register. These systems have the following IDs and
ROM family types:
System System ID ROM Family PnP ID
Small Form Factor:
w/815E-based graphics
w/NVIDIA graphics
688h
680h
686P2
686P3
CPQ0004
CPQ0003
Slim Desktop/Configurable Minitower 684h 686P2 CPQ0005
The ROM family and version numbers can be verified with the Setup utility or the Compaq
Insight Manager or Diagnostics applications.
8.5.2 EDID RETRIEVE
The BIOS function INT 15, AX=E813h is a tri-modal call that retrieves the VESA extended
display identification data (EDID). Two subfunctions are provided: AX=E813h BH=00h retrieves
the EDID information while AX=E813h BX=01h determines the level of DDC support.
Input:
AX = E813h
BH = 00 Get EDID .
BH = 01 Get DDC support level
If BH = 00 then
DS:(E)SI = Pointer to a buffer (128 bytes) where ROM will return block
If 32-bit protected mode then
DS:(E)SI = Pointer to $DDC location
Output:
(Successful)
If BH = 0:
DS:SI=Buffer with EDID file.
CX = Number of bytes written
CF = 0
AH =00h Completion of command
If BH = 1:
BH = System DDC support
<0>=1 DDC1 support
<1>=1 DDC2 support
BL = Monitor DDC support
<0>=1 DDC1 support
<1>=1 DDC2 support
<2>=1 Screen blanked during transfer
(Failure)
CF = 1
AH = 86h or 87h
Compaq Deskpro and Evo Personal Computers
Featuring Intel Celeron and Pentium III Processors
Fifth Edition - March 2002
8-14
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