What are the five optional features of Ultra 160 (Ultra 3) SCSI?
• Answer: As defined in the SPI-3 document of SCSI-3, they are: Double Transition Clocking, CRC, Domain Validation, Quick Arbitration and Select (QAS), and Information Units (Packetization). In order to be compliant with the SPI-3 U160 specification, at least one of these features must be implemented. A group of industry leaders agreed to incorporate three of these features in order to speed up introduction of U160 products and to simplify backward compatibility. These three features are Double Transition Clocking, CRC and Domain Validation. U160 devices with these three features are called U160/m.