HP Vectra Technical Reference Manual page 375

EX-BIOS Data Area layout
HP_VECTOR_TABLE
HP_ENTRY's CS:O
HP_ENTRY_CODE
HP_ENTRY's CS:IP
"Max OS"
"Last used OS"
TOP of RAM
HP_VECTOR_TABLE
HP_ENTRY_CODE
EX-BIOS
Memory
Pool
-
EX-BIOS Resident
Driver's Data
Segments
EX-BIOS Global
Data Segment
Figure B.1
EX-BIOS
Memory
Pool
b. This address is the offset {IP) value stored in the first word of the HP_ENTRY interrupt
vector 06FH. This address (CS:IP) represents the end of the HP_VECTOR-TABLE and
~
points to the EX-BIOS's HP_ENTRY_CODE.
c. This address represents the last allocatable data segment ("MAX DS") value available from
the EX-BIOS memory pool. This address may be obtained as well as allocated from the EX-
BIOS V_SYSTEM driver, see F_RAM_GET and F_RAM_RET in Section 9.
d. This address is passed to drivers requesting memory from the EX-BIOS memory pool. Drivers
must first subtract the size of their data segment from the "Iast used DS" value to get an
addressable data area. The new "Iast used DS" is returned to the EX-BIOS using the
F_RAM_RET function.
e. This address represents the EX-BIOS global data area used by drivers and services that share
data. This address is the DS value stored in the HP_VECTOR-TABLE for the V_SYSTEM
driver.
f. Top of RAM is the last address in memory. In a 256KB system this value is 3FFFFH while in a
640KB system this value is 9FFFFH. The data region between Top of RAM and the base of
HP_VECTOR-TABLE is not directly available to applications. In the base system this region
is 4KB long. However, different system configurations may require that this region be
lengthened.
366 Memory Map