A computer system includes a CPU and a memory device coupled by a North
bridge logic unit to an expansion bus, such as a PCI bus. A South bridge
logic connects to the expansion bus and couples various secondary busses
and peripheral devices to the expansion bus. The South bridge logic
includes internal control devices that are targets for masters on the
expansion bus. The target devices couple to the expansion bus through a
common expansion target interface, which monitors and translates master
cycles on the expansion bus on behalf of the target devices. The South
bridge also includes an internal modular target expansion bus coupling the
internal target devices to the common target interface. The internal
modular target expansion bus permits the target devices to receive master
cycles from any expansion bus by understanding a standardized group of
signals represented by the internal modular target expansion (IMAX) bus.
The target interface then is responsible for understanding the protocol of
the expansion bus and converting the expansion bus signals to IMAX target
bus signals. The IMAX target bus includes both an inbound bus and an
outbound data bus for driving out data requested as part of a read cycle
to an internal target device.