System Address Map

Figure 4-1. System Memory Address Space

 

High

 

Extended

(16 TB-4GB)

Memory

(4 GB-16MB)

Medium

 

Extended

 

memory

 

 

 

Low

15 MB

Extended

Memory

 

 

 

1 MB

Compatibility

Area

 

FFF_FFFF_FFFF

FFFF_FFFF

 

System

 

 

 

 

 

 

Memory

 

 

 

High

 

 

 

 

 

 

System

 

 

 

 

 

 

Firmware

 

 

 

 

FF00_0000

 

 

 

1_0000_0000

 

 

 

Processor

 

 

 

 

 

 

 

 

 

FEC0_0000

Specific

 

 

 

 

 

 

 

Firmware,

32

Chipset

 

 

 

 

 

 

Processor &

 

 

 

 

Chipset

MB

 

 

Specific

 

 

Specific

 

FE00_0000

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

n x 32M

 

 

 

 

 

 

 

 

 

 

FE00_0000 -

PCI Gaps

 

 

System

 

 

 

 

 

(n x 32M)

 

 

Memory

 

 

 

 

 

10_0000

System 64K

Firmware

F_0000

C, D, and E

16 MB

4MB

12 MB

Areas are not drawn to scale.

Segments

C_0000

192K

VGA 128K

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