Computer system with bridge logic that includes an internal modular expansion bus and a common master interface for internal master devices

Abstract

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 or master devices that are designed to run master cycles on the expansion bus. The master devices couple to the expansion bus through a common expansion master interface, which executes master cycles on the expansion bus on behalf of the master devices. The South bridge also includes an internal modular master expansion bus coupling the internal master devices to the common master interface. The internal modular master expansion bus permits the master devices to run master cycles to any expansion bus by understanding a standardized group of signals represented by the internal modular master expansion (IMAX) bus. The master interface then is responsible for understanding the protocol of the expansion bus and converting the IMAX master bus signals to signals compatible with the expansion bus. In addition, a dedicated target IMAX bus may also be provided for coupling internal targets within the South bridge to masters on the expansion bus through a common expansion target interface.