main contents:
describe the purpose and function of the UPA bus
describe the purpose and function of the PCI bus
describe the purpose and function of the SCSI bus
describe the purpose and function of the Fibre Channel interface

The Ultra Port Architecture(UPA) supports the high-performance UltraSPRAC design. Sun Microsystems created this new component interconnect bus to optimize data transfers between devices and system boards. designed specifically for multitasking,multiprocessing environments, the UPA interconnect handles multiple simultaneous requests for data transfers between processors, memory, and I/O devices

UPA features include:
packet-switched bus
high speed(1.6 Gbytes/second)
high bandwidth
direct CPU to memeory without crossbar switching
improved 3D graphics acceleration

This new high-performance architecture has a processor-to-memory interconnect using the UPA bus.The UPA bus runs at one-half the CPU clock rate because it is twice as wide.This enables the CPU to load each half of the bus's data before the next bus cycle Sun Microsystems designed the SunBus(SBus) to provide the SPARC products with a high-performance, space-efficient, and cost effective system bus.
SBus provides for device autoconfiguration. Installing SBus expansion boards is easy because of an EPROM containing machine-independent forth code that describes the board's function and contains a POST that is compatible with Sun systems POST commands

Peripheral Component Interconnect(PCI) offers many of the same characteristics as SBus, and is an open standard that Sun Microsystems has chosen to support for a variety of reasons
There are three distinct address domains in the PCI bus architecture:
configuration,memory,and I/O
On Ultra servers, the PCI supports dual PCI domains. One is a 64-bit, 66MHz bus,while the second is a 64-bit,33MHz bus.The 66MHz version uses a 3.3 volt connector while the 33MHz use a 5 volt connector

The small computer system interface(SCSI)-1 standard defines two modes of data transfer:
asynchronous(异步) and synchronous(同步) mode. SCSI-1 synchronous transfer rates are limited to 5M/S.
The SCSI-2 standard defines an option known as Fast SCSI, which increases the synchronous transfer rate to 10M/S. The terms Fast SCSI and 10-Mbyte SCSI are synonymous
The SCSI standard defines two types of electrical interfaces: single-ended and differential. Single-ended uses a 50-pin, differential uses a 68-pin
SCSI-3 is also known as Ultra-SCSI,it combines the features of Fast SCSI with Wide SCSI and doubles the transfer rate to 40M/S
Ultra 2 SCSI is the latest of the SCSI standard. it provides up to 80M/S

The current high speed disk subsystem connection device is the gigabit interface converter(GBIC). this is hot swappable module provides a 100M/S