Intel PCI User Manual

204

Many of the fields of the PCI header space contain hardware default values that are either fixed or 

can be overridden using EEPROM, but cannot be independently specified for each logical LAN 

device. The following fields are considered to be common to both LAN devices:

24h

Base Address 5

28h

Cardbus CIS Pointer (not used)

2Ch

Subsystem ID

Subsystem Vendor ID

30h

Expansion ROM Base Address

34h

Reserved

Cap_Ptr

38h

Reserved

3Ch

Max_Latency 00h

Min_Grant 

FFh

Interrupt Pin

01h or 00h)

Interrupt Line

00h

Vendor ID

The Vendor ID of the Ethernet controller can be specified via EEPROM, but 
only a single value can be specified. The value is reflected identically for both 
LAN devices.

Revision

The revision number of the Ethernet controller is reflected identically for both 
LAN devices.

Header Type

This field indicates if a device is single function or multifunction. The value 
reflected in this field is reflected identically for both LAN devices, but the actual 
value reflected depends on LAN Disable configuration.
When both Ethernet controller LAN ports are enabled, both PCI headers return 
80h in this field, acknowledging being part of a multi-function device. LAN A 
exists as device “function 0”, while LAN B exists as device “function 1”.
If one of the LAN ports is disabled, then only a single-function device is 
indicated (this field returns a value of 00h), and the LAN exists as device 
“function 0”.

Subsystem ID

The Subsystem ID of the Ethernet controller can be specified via EEPROM, 
but only a single value can be specified. The value is reflected identically for 
both LAN devices.

Subsystem Vendor ID

The Subsystem Vendor ID of the Ethernet controller can be specified via 
EEPROM, but only a single value can be specified. The value is reflected 
identically for both LAN devices.

Class Code,
Cap_Ptr,
Max Latency,
Min Grant

These fields reflect fixed values that are constant values reflected for both LAN 
devices.