Technical Q&A

HW 79 - What is a CardBus host bus adapter HBA? (15-November-1999)

Q: What is a CardBus host bus adapter, HBA, and how is it implemented on the Macintosh?

A: A CardBus HBA is a PCI-to-CardBus bridge as implemented on a Macintosh. The socket or sockets are the PCI function or functions. If there is more than one socket, say two, then the CardBus bridge is a PCI multifunction device. The PCI Specification defines multifunction ordinals starting at 0 and increasing by 1 for each additional function. As is true for all PCI devices, there can be no more than 8 functions per device. There can be 32 devices per bus and, of course, 256 buses in a complete PCI Domain.