Editing PCI configuration space (section)

== Standardized registers ==
[[Image:Pci-config-space.svg|thumb|300px|right|Standard registers of PCI Type 0 (Non-Bridge) Configuration Space Header]]

The ''Device ID (DID)'' and ''Vendor ID (VID)'' registers identify the device (such as an [[integrated circuit|IC]]), and are commonly called the ''PCI ID''. The 16-bit vendor ID is allocated by the [[PCI-SIG]]. The 16-bit device ID is then assigned by the vendor. There is an inactive project to collect all known Vendor and Device IDs. (See the [[#External links|external links]] below.)

The ''Status'' register is used to report which features are supported and whether certain kinds of errors have occurred. The ''Command'' register contains a bitmask of features that can be individually enabled and disabled. The ''Header Type'' register values determine the different layouts of remaining 48 bytes (64-16) of the header, depending on the function of the device. That is, Type 1 headers for Root Complex, switches, and bridges. Then Type 0 for endpoints. The ''Cache Line Size'' register must be programmed before the device is told it can use the memory-write-and-invalidate transaction. This should normally match the [[CPU cache|CPU's cache]] line size, but the correct setting is system dependent. This register does not apply to PCI Express.

The ''Subsystem ID (SSID)'' and the ''Subsystem Vendor ID (SVID)'' differentiate specific model (such as an add-in card). While the Vendor ID is that of the [[chipset]] manufacturer, the Subsystem Vendor ID is that of the card manufacturer. The Subsystem ID is assigned by the subsystem vendor, the Device ID is assigned by the chipset manufacturer. As an example, in the case of [[Wireless network interface controller|wireless network cards]], the chip manufacturer might be [[Intel Corp|Intel]] or [[Broadcom]] or [[Atheros]], and the card manufacturer might be [[Netgear]] or [[Hewlett-Packard]]. Generally, the Vendor ID&ndash;Device ID combination designates which [[Device driver|driver]] the host should load in order to handle the device, as all cards with the same VID:DID combination can be handled by the same driver. The Subsystem Vendor ID&ndash;Subsystem ID combination identifies the card, which is the kind of information the driver may use to apply a minor card-specific change in its operation.