82845MP datasheet(39/157 Pages) INTEL

39 / 157 page

Intel

® 82845MP/82845MZ Chipset-Mobile (MCH-M)

250687-002

Datasheet

“Reserved” register location is read, a random value is returned. (“Reserved” registers can be 8-bit, 16-

bit, or 32-bit in size.) Writes to “Intel Reserved” registers may cause system failure. Reads to “Intel

Reserved” registers may return a non-zero value.

Default Value Upon Reset:

Upon a full Reset, the MCH-M sets all of its internal configuration registers to predetermined default

states. Some register values at reset are determined by external strapping options. The default state

represents the minimum functionality feature set required to successfully bring up the system. Hence, it

does not represent the optimal system configuration. It is the responsibility of the system initialization

software (usually BIOS) to properly determine the DRAM configurations, operating parameters and

optional system features that are applicable, and to program the MCH-M registers accordingly.

3.5.

I/O Mapped Registers

The MCH-M 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.

3.5.1.

CONFIG_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

1 0

Reserved

Function Number

Device Number

Bus Number

Reserved

Enable

Bit

Default

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