Register and Memory Mapping
5.3.1
Legacy Video Area (A0000h – BFFFFh)
The legacy 128 KB VGA-memory range can be mapped to the Intel Graphics Media
Adapter (Device 2) or forwarded to an external graphics device located on one of the
two PCI Express I/O ports. The VGA-Disable bit in the Graphics Control register of the
Intel Graphics Media Adapter PCI config space can be set to ignore VGA memory or I/O
cycles. If that bit is set, the Intel® SCH will steer VGA accesses to the appropriate PCI
Express port. If such a device does not exist in the system, the cycles will be ignored.
5.3.2
5.3.3
5.3.4
Expansion Area (C0000h – DFFFFh)
This 128-KB ISA-Expansion region is always mapped to DRAM. This region is typically
used by BIOS to shadow (copy) option ROMs, including Video BIOS. This region cannot
be write protected.
Extended System BIOS Area (E0000h – EFFFFh)
This area is a single, 64-KB segment that can be assigned independent read/write
attributes and is mapped only to main DRAM Typically, this area is used for RAM or
ROM. Memory segments that are disabled are not remapped elsewhere.
System BIOS Area (F0000h – FFFFFh)
This area is a single, 64-KB segment that can be assigned read and write attributes.
After reset, this region defaults to “disabled” and cycles are forwarded to the LPC
interface. By manipulating the Read/Write attributes of this memory range, the Intel®
SCH can “shadow” BIOS into the main DRAM. When disabled, this segment is not
remapped.
5.3.5
5.3.6
EHCI Controller Area
The EHCI controller (Device 29, Function 7) requires a single, 1-KB to be reserved out
of the 1-GB main memory area for configuration purposes. See Chapter 13 for more
details.
Programmable Attribute Map (PAM)
The two, 64-KB memory regions below 1-MB comprise the PAM Memory Area. See
Table 11 for these ranges and default attributes.
Any attempts by the processor or an Intel® SCH device to read a segment marked with
the Read Disable attribute will return undefined data.
Table 11.
Programmable Attribute Map
Default
Region
Memory Segments
Attributes
“Segment E”
“Segment F”
0E0000h – 0EFFFFh
0F0000h – 0FFFFFh
R/W
WE RE
62
Datasheet
INTEL [ INTEL ]
