The BRIDGE ASIC is used as the PCI hostbridge in the SGI IP27 family of machines. It interfaces between the internal Crosstalk connect one the one side and the 64-bit, 33MHz PCI bus on the other side. It supports 32-bit PCI cards by providing an address translation mechanism allowing 32-bit PCI cards to access the entire 64-bit address space of the system. BRIDGE also allows to specify a few attributes in 64-bit DMA addresses rsp. the address translation tables allowing to maximize performance.
Linux support BRIDGE but is currently limited to 64-bit cards only.