PCI Express System Architecture

ROM Content

Multiple Code Images

The PCI spec permits the inclusion of more than one code image in a PCI device ROM. Each code image would contain a copy of the device driver in a specific machine code, or in interpretive code (explained later). The configuration software can then scan through the images in the ROM and select the one best suited to the system processor type. The ROM might contain drivers for various types of devices made by this device's vendor. The code image copied into main memory should match up with the function's ID. To this end, each code image also contains:

• the Vendor ID and Device ID. This is useful for matching up the driver with a function that has a vendor/device match.

• the Class Code. This is useful if the driver ...