System Address Map

Figure 4-1. System Memory Address Space

(16 TB-4GB)

(4 GB-16MB)

15 MB

1 MB

High

Extended

Memory

Medium Extended memory

Low

Extended

Memory

Compatibility

Area

FFF_FFFF_FFFF

System

Memory

1_0000_0000

Firmware,

Processor &

Chipset

Specific

System

Memory

10_0000

FFFF_FFFF

FF00_0000

FEC0_0000

32 MB

FE00_0000

FE00_0000 - (n x 32M)

High

System

Firmware

Processor Specific

Chipset Specific

n x 32M PCI Gaps

16 MB

4MB

12 MB

Areas are not drawn to scale.

 

 

 

 

 

System

64K

 

 

 

 

 

Firmware

F_0000

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

C, D, and E

192K

 

 

 

 

 

 

 

 

 

 

 

Segments

 

 

 

 

 

 

 

C_0000

 

 

 

 

 

 

 

 

 

128K

 

 

VGA

 

 

 

 

 

 

 

 

 

 

 

 

Memory

 

A_0000

 

 

 

 

 

 

 

 

 

 

 

512K-640K

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DOS

 

 

 

 

 

 

 

Region

640K

0

4.1.1.4System Firmware

The 64 KB region from F_0000h to F_FFFFh is treated as a single block. Read/Write attribute enables defined in the MAR registers may be used to direct accesses to the compatibility PCI bus or main memory. At power-on, this area is mapped by default to the PCI compatibility bus.

4-2

Intel® 460GX Chipset Software Developer’s Manual

Page 82
Image 82
Intel 460GX manual System Firmware, System Memory Address Space