Technical Information 1-11
Table Section 1-2 System Memory Map
Memory Space
Size
Function
000000-07FFFF
512 KB
Conventional base memory
080000-09FBFF
127 KB
Extended conventional base memory
09FC00-09FFFF
1 KB
Extended BIOS Data (movable by EMM386, QEMM and 386
max)
0A0000-0BFFFF
128 KB
On-board video memory
0C0000-0C7FFF
32 KB
On-board video BIOS
0C8000-0DFFFF
128 KB
Open to EISA and PCI bus*
**E0000-FFFFF
128 KB
System BIOS
100000- On-Board
255 MB
Extended system memory
* On-board Adaptec PCI SCSI-2 bus may use 10 to 32 KB of this area
**
Detail map of E0000-FFFFF:
E0000 - E324F
available, not used
***
E3250 - E477F
Setup
E4780 - E536F
BIOS string table
E5370 - EC5B6
Plug and Play code
EC5B7 - FFFFF remainder of BIOS
**
Subject to change without notice
*** May be reclaimed for DOS UMB’s (include E000 - E4FF)
Flash ROM supports the reprogramming of the system and built-in video BIOS. The Flash
part can be accessed in 128K granularity for ROM reads and 64K granularity for flashing.
NEC Port 0C12h bits 6 and 7 map each of the four 64K byte chunks of the ROM to the
FXXXX range. ACU access is controlled by the system BIOS code and is generally not
accessible in ISA space. Table Section 1-3 shows how to access the different areas of the
Flash ROM by using bits 6 and 7 (RPG0 – 1) from NEC proprietary port 0C12h (see “NEC
Proprietary Ports” later in this section).
Table Section 1-3 Flash ROM Selection Bits
RPG0
RPG1
Selection
0
0
Highest 64 KB accessible at FXXXX
0
1
Third 64 KB accessible at FXXXX
1
0
Second 64 KB accessible at FXXXX
1
1
Lowest 64 KB accessible at FXXXX