Compaq Deskpro 4000 Technical Reference Manual page 162

Chapter 8 BIOS ROM
To support Windows NT an additional table to the BIOS32 table has been defined to contain 32-
bit pointers for the DDC and SIT locations. The Windows NT extension table is as follows:
; Extension to BIOS SERVICE directory table (next paragraph)
db
db
db
dd
dw
db
dd
dw
db
dd
dw
The service identifier for Client Management functions is "$CLM." Once the service identifier is
found and the checksum verified, a FAR call is invoked using the value specified at offset 04h to
retrieve the CM services entry point. The following entry conditions are used for calling the
Client Management service directory:
INPUT:
EAX
EBX (31..8)
EBX (7..0)
CS
DS
SS
(I/O permissions must be provided so that the BIOS can support as necessary)
OUTPUT:
AL
EBX
ECX
EDX
The following subsections describe aspects of Client Management unique to this system. For a
general description of these BIOS functions refer to the Compaq BIOS Technical Reference
Guide.
8-6 Compaq Deskpro 4000 and 6000 Personal Computers
featuring the Pentium II Processor
"32OS" ; sig
2 ; number of entries in table
"$DDC" ; DDC POST buffer sig
? ; 32-bit pointer
? ; byte size
"$SIT" ; SIT sig
? ; 32-bit pointer
? ; byte size
"$ERB" ; ESCD sig
? ; 32-bit pointer
? ; bytes size
= Service Identifier [$CLM]
= Reserved
= Must be set to 00h
= Code selector set to encompass the physical page holding
entry point as well as the immediately following physical page.
It must have the same base. CS is execute/read.
= Data selector set to encompass the physical page holding
entry point as well as the immediately following physical page.
It must have the same base. DS is read only.
= Stack selector must provide at least 1K of stack space and be 32-bit.
= Return code:
00h, requested service is present
80h, requested service is not present
81h, un-implemented function specified in BL
86h and CF=1, function not supported
= Physical address to use as the selector BASE for the service
= Value to use as the selector LIMIT for the service
= Entry point for the service relative to the BASE returned in EBX
First Edition – October 1997