Compaq ProLiant 8000 Compaq ProLiant 8000 Server Technology - Page 9

TC000603TB TECHNOLOGY BRIEF (cont.) ... PCI Hot Plug Technology The host-to-PCI bridges include electronics to support PCI Hot Plug technology, which was pioneered by Compaq. PCI Hot Plug technology provides the ability to remove, replace, upgrade, and add PCI adapters without shutting down the server. Any PCI adapter can be placed in a PCI Hot Plug slot; however, PCI Hot Plug device drivers and OS support are required to enable PCI Hot Plug functionality. Peer-to-Peer Transactions The host-to-PCI bridges also support PCI peer-to-peer transactions. They allow communications between two devices on the same PCI bus segment. They also allow communication across the I/O bus between PCI devices on different PCI bus segments (Figure 4). Processor Bus I/O 100 MHz Bus Host-to-PCI Bridge Host-to-PCI Bridge PCI Bus PCI Bus PCI Device 1 PCI Device 4 PCI Device 2 PCI Device 5 PCI Device 3 Figure 4: Schematic of peer-to-peer communications between PCI devices on different I/O bus segments. Microprocessors embedded in the PCI devices make these devices "intelligent" and perform the communication tasks otherwise handled by the processors. Thus, the host-to-PCI bridges enhance performance by freeing the system processors to do other work. 9