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[ The PC Guide | Systems and Components Reference Guide | Hard Disk Drives | Hard Disk Interfaces and Configuration | Small Computer Systems Interface (SCSI) | SCSI Protocols and Interface Features ]

Packetization

While the SCSI interface is widely implemented on high-end hardware due to its flexibility and high performance, its complexity does mean that some of its potential performance is lost to overhead. In an effort to improve SCSI bus performance by reducing overhead, the SPI-3 SCSI standard describes a new feature that is generally called packetization or packetized SCSI.

Packetization is a technique whereby some of the phases that are involved in setting up a command request and data transfer are combined. For example, under traditional SCSI interfacing, several different types of information are sent over the bus separately: commands, data, status messages and so on. With packetization, these are grouped together into packets (also called information units) and sent as a single entity. This reduces some of the wasted bus cycles normally sent on managing all the individual transfers in regular SCSI.

Packetization is one of the five "optional" features of Ultra3 SCSI. It was not included as one of the required features for hardware meeting the Ultra160 specification, but is present in Ultra160+ devices. It may also be part of the requirements for Ultra320 SCSI when that specification is complete.

Next: SCSI Protocol Map


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