PCI Express System Architecture

I/O Bus Architecture Perspective

33 MHz PCI Bus Based System

Figure 1-2 on page 17 is a 33 MHz PCI bus based system. The PCI system consists of a Host (CPU) bus-to-PCI bus bridge, also referred to as the North bridge. Associated with the North bridge is the system memory bus, graphics (AGP) bus, and a 33 MHz PCI bus. I/O devices share the PCI bus and are connected to it in a multi-drop fashion. These devices are either connected directly to the PCI bus on the motherboard or by way of a peripheral card plugged into a connector on the bus. Devices connected directly to the motherboard consume one electrical load while connectors are accounted for as 2 loads. A South bridge bridges the PCI bus to the ISA bus where slower, lower performance peripherals ...