Register Description

system initialization software (usually BIOS) to properly determine the DDR SDRAM configurations, operating parameters, and optional system features that are applicable and to program the GMCH registers accordingly.

4.6I/O Mapped Registers

The GMCH contains two registers that reside in the CPU I/O Address Space: the Configuration Address (CONFIG_ADDRESS) Register and the Configuration Data (CONFIG_DATA) Register. The Configuration Address Register enables/disables the Configuration Space and determines what portion of Configuration Space is visible through the Configuration Data window.

4.6.1CONFIG_ADDRESS – Configuration Address Register

I/O Address:

0CF8h Accessed as a Dword

Default Value:

00000000h

Access:

Read/Write

Size:

32 bits

CONFIG_ADDRESS is a 32-bit register that can be accessed only as a Dword. A Byte or Word reference will “pass through” the Configuration Address Register and the Hub interface, onto the PCI bus as an I/O cycle. The CONFIG_ADDRESS register contains the Bus Number, Device Number, Function Number, and Register Number for which a subsequent configuration access is intended.

Figure 2. Configuration Address Register

31 30

 

24

23

16

15

11 10

8 7

2

1 0

0

R

 

 

0

 

0

0

 

0

R

 

 

 

 

 

 

 

 

 

 

 

Bit

Default

Reserved

Register Number

Function Number

Device Number

Bus Number

Reserved

Enable

D15343-003

45

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Intel D15343-003 manual I/O Mapped Registers, Configaddress Configuration Address Register