450NX Datasheet, PDF (82/248 Pages) Intel Corporation – Intel 450NX PCIset

4. System Address Maps
F_FFFF_FFFF
64 GB
FFE0_0000
20 MB Total
High BIOS
2 MB
14 MB
1_0000_0000
High ^{4 GB}
Compatibility
Region
FEF0_0000
FEE0_0000
FEC0_0000
Local APIC
Reserved
I/O APIC
1 MB
1 MB
1 MB
1 MB
Top of
Memory
Local PCI Bus 1b
Local PCI Bus 1a
Local PCI Bus 0b
Local PCI Bus 0a
High
Expansion
Gap
100_0000
16 MB
Low ISA Space
Low
Expansion
Gap
10_0000
0
Low ^{1 MB}
Compatibility
Region
Areas are not
drawn to scale.
F_0000 ^{System BIOS 64K}
E_0000 ^{Ext System BIOS 64K}
C_0000
A_0000
ISA Expansion
Graphics Adapter
Memory
128K
128K
DOS Region 640K
ISA
96KB
C_8000 ^{Channel I/O}
Video BIOS ^32KB
8_0000 ^{ISA Window 128KB}
DOS Area ^512KB
0
Figure 4-1: System Memory Address Space
• The 128 KB ISA Expansion Region is divided into eight 16 KB blocks that can be
independently configured for read/write accessibility. Typically, these blocks are
mapped through the PCI bridge to ISA space. Memory that is disabled is not remapped.
Traditionally, the lower 32 KB contains the video BIOS located on a video card, and the
upper 96 KB is made available to expand memory windows in 16 KB blocks depending on
the requirements of other channel devices in the corresponding ISA space.
• The 64 KB Extended System BIOS Region is divided into four 16 KB blocks and may be
mapped either to memory or the compatibility PCI bus. Typically, this area is used for
RAM or ROM. Selecting appropriate read/write attributes for this region allows the BIOS
to be “shadowed” into RAM.
4-2
Intel® 450NX PCIset