The information to be populated into the Predefined Devices object class is described in the Predefined Devices (PdDv) Object Class. The following descriptors should be set as indicated:
| Item | Description |
|---|---|
| Device Class | Set to adapter. |
| Device ID | Must identify the values that are obtained from the POS(0) and POS(1) registers on the adapter card. The format is 0xAABB, where AA is the hexadecimal value obtained from POS(0), and BB the value from POS(1). This descriptor is used by the Bus Configurator to match up the physical device with its corresponding information in the Configuration database. |
| Bus Extender Flag | Usually set to FALSE, which indicates that the adapter card is not a bus extender. This descriptor is set to TRUE for a multi-adapter card requiring different sets of bus resources assigned to each adapter. The Standard I/O Planar is an example of such a card. |
The Bus Configurator behaves slightly differently for cards that are bus extenders. Typically, it finds an adapter card and returns the name of the adapter to the Configuration Manager so that it can be configured.
However, for a bus extender, the Bus Configurator directly invokes the device's Configure method. The bus extender's Configure method defines the various adapters on the card as separate devices (each needing its own predefined information and device methods), and writes the names to standard output for the Bus Configurator to intercept. The Bus Configurator adds these names to the list of device names for which it is to assign bus resources.
An example of a type of adapter card that would be a bus extender is one which allows an expansion box with additional card slots to be connected to the system.