IBM B50 manual

The AB value identifies a bus type or PCI parent bus as assigned by the firmware.

The CD value identifies adapter number, adapter's devfunc number, or physical location. The devfunc number is defined as the PCI device number times 8, plus the function number.

The EF value identifies a connector.

The GH value identifies a port, address, device, or FRU.

Adapters and cards are identified with AB-CD.

The possible values for AB are:

00Processor bus

01ISA bus

02EISA bus

03MCA bus

04PCI bus used in the case where the PCI bus cannot be identified

05PCMCIA buses

xy	For PCI adapters where x is equal to or greater than 1. The x and y are
	characters in the range of 0-9, A-H, J-N, P-Z (O, I, and lowercase are
	omitted) and are equal to the parent bus's ibm, aix-loc Open Firmware
	Property.

The possible values for CD depend on the adapter/card:

For pluggable PCI adapters/cards, CD is the device's devfunc number (PCI

device number times 8, plus the function number). The C and D are characters

in the range of 0-9, and A-F (hex numbers). Location codes therefore uniquely identify multiple adapters on individual PCI cards.

For pluggable ISA adapters, CD is equal to the order the ISA cards defined/configured either by SMIT or the ISA Adapter Configuration Service Aid.

For integrated ISA adapters, CD is equal to a unique code identifying the ISA adapter. In most cases, this code is equal to the adapter's physical location code. In cases where a physical location code is not available, CD is FF.

EF is the connector ID, used to identify the adapter's connector to which a resource is attached.

GH is used to identify a port, device, or FRU. For example:

4-47046 Model B50 Service Guide