Avago Technologies LSI21040 - Manual (Page 15)

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Benefits of Ultra160 SCSI 1-5
1.3 Benefits of Ultra160 SCSI
Ultra160 SCSI delivers data up to two times faster than Ultra2 SCSI.
Ultra160 SCSI is a subset of the SCSI Parallel Interface-3 (SPI-3) draft
standard that allows faster synchronous SCSI data transfer rates than
Ultra2 SCSI. When enabled, Ultra160 SCSI performs 80 megatransfers
per second resulting in approximately double the synchronous data
transfer rates of Ultra2 SCSI. The LSI53C1010 performs 16-bit, Ultra160
SCSI synchronous data transfers as fast as 160 Mbytes/s. This
advantage is most noticeable in heavily loaded systems or large block
size applications, such as video on-demand and image processing.
1.3.1 Double Transition (DT) Clocking
Ultra160 SCSI includes DT clocking in order to double data transfer
speeds without increasing the clock rate. As a result, data is clocked on
both rising and falling edges of the Request and Acknowledge signals.
1.3.2 Cyclic Redundancy Check (CRC)
Ultra160 SCSI includes CRC to provide data bus protection. CRC offers
higher levels of data reliability by ensuring complete integrity of
transferred data. CRC is a 32-bit scheme, referred to as CRC-32. CRC
is guaranteed to detect all single bit errors, all double bit errors, or any
combination of errors within a single 32-bit range.
1.3.3 Domain Validation
Ultra160 SCSI also includes Domain Validation to provide basic integrity
checking. Domain Validation is a procedure that allows a host computer
and target SCSI peripheral to negotiate and find the optimal transfer
speed. This procedure improves overall reliability of the system.
SURElink™ extends this feature by providing three levels of integrity
checking. Refer to
Section 1.6, “Benefits of SURElink (Extended Domain
Validation),” on page 1-7 for more detailed information.