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SCSI(-3) Parallel Interface - 3 (SPI-3)
The third generation of the SCSI parallel interface is, unsurprisingly, called the SCSI(-3) Parallel Interface - 3 or SPI-3. This document builds upon the physical and protocol definitions of the SPI-2 document. It is in the process of approval at the time of this writing, so it has no ANSI standard number yet, but should be published by early 2001 (it's T10 project 1302-D).
Five main features were added to parallel SCSI in the SPI-3 standard:
Other, smaller changes were also made. SPI-3 also does some "cleanup" of the parallel SCSI standard, by making obsolete several older features that either never caught on in the industry, or were replaced with superior ways of accomplishing the same tasks:
Unfortunately, despite the lessons that should have been learned in the past regarding what happens when standards aren't kept universal, the SCSI industry managed to create another mess out of the SPI-3 standard. The SCSI Trade Association defined the marketing term "Ultra3 SCSI" to correspond to the features introduced in SPI-3. However, they allowed a device that implemented any sub-set of the five main new features to be called "Ultra3 SCSI"; this "optionality" meant that there was no guarantee that any two devices labeled "Ultra3 SCSI" had the same features! Hardware manufacturers didn't like this, so they decided to market alternative names for more concrete subsets of the Ultra3 features, and we were off to the competing standards races yet again. The results were Ultra160 and Ultra160/m SCSI, and Ultra160+ SCSI.
(Someday, all these companies will get their act together and these things won't happen any more--and I'll probably die of shock. ;^) )