PCI Express System Architecture

Header Type 1

General

Figure 22-13 on page 803 illustrates the layout of a PCI-to-PCI bridge's configuration header space.

Header Type 1 Registers Compatible With PCI

The Header Type 1 PCI configuration registers that are implemented and used identically in both PCI and PCI Express are:

• Vendor ID register.

• Device ID register.

• Revision ID register.

• Class Code register.

• Header Type register.

• BIST register.

• Capabilities Pointer register.

• Subordinate Bus Number register.

• Secondary Bus Number register.

• Primary Bus Number register.

• IO Base, Limit and Upper registers.

• Memory Base and Limit registers.

• Expansion ROM Base Address register.

The sections that follow provide a description of each of these registers.

Header Type 1 Registers Incompatible With PCI

In a ...