Sun Microsystems 280R manual About Peripheral Component Interconnect PCI Buses

About Peripheral Component

Interconnect (PCI) Buses

All system communication between the CPU/memory subsystem and all external devices, network interfaces and internal storage/removable media is handled by the host-bus to PCI-bridge application specific integrated circuit (ASIC). This bridge ASIC manages communication between the system bus and the two PCI buses. These PCI buses support slots for up to four PCI interface cards. One PCI bus (bus

A)also handles communication between the system and the on-board Fibre Channel-Arbitrated Loop (FC-AL) controller for the internal drives and the external high-speed serial data connector (HSSDC). The other PCI bus (bus B) handles communication between the system and the main logic board’s SCSI controller, Ethernet controller, Universal Serial Bus (USB) controller, and serial and parallel port controller.

PCI cards are available in a variety of configurations. Not all cards will fit or operate in all PCI slots, so it is important to know the specifications of your PCI cards and the types of cards supported by each PCI slot in the system.

Some PCI cards are as short as 6.875 inches (17.46 cm) in length (called “short” cards), while the maximum length of PCI cards is 12.28 inches (31.19 cm, called “long” cards). Each slot in the system can accommodate either a long or a short card.

Older PCI cards communicate over 32-bit PCI buses, while many newer cards communicate over wider 64-bit buses. All four of the PCI slots accept either 32-bit or 64-bit wide cards.

Older PCI cards operate at 5 VDC, while newer cards are designed to operate on

3.3VDC. Cards that require 5 volts will not operate in 3.3-volt slots, and 3.3-volt cards will not operate in 5-volt slots. “Universal” PCI cards are designed to operate on either 3.3 volts or 5 volts, so these cards can be inserted into either type of slot. The system provides three slots for 5-volt cards and one slot for a 3.3-volt card.

All four PCI slots accept universal cards.

Most PCI cards operate at clock speeds of 33 MHz, while some newer cards operate at 66 MHz. All four PCI slots can accept 33-MHz cards. 66-MHz cards are restricted to the slot labeled PCI 1.

84 Sun Fire 280R Server Owner’s Guide • January 2001