Low Density connector for SCSI-3

[Gerry Houlder]

* From the SCSI Reflector, posted by:
* Gerry Houlder <Gerry_Houlder at notes.seagate.com>
*
The only 68 pin connector allowed for SCSI is the high density connector 
described in SCSI-3 SPI document. This is the only 68 pin connector for market 
acceptance reasons. If other 68 pin connectors were allowed this would fragment 
the market into connector type segments.

This connector is not is SCSI-2 because the connector was not agreed upon until 
after the cutoff date for inclusion in SCSI-2. The B connector (which allows 
expansion for 3 additional data bytes) that is described in SCSI-2 was not 
successful in the market place and is not recommended for new designs.

There is also an SCA (single connector attach) connector that was defined in 
the SFF industry group. This is an 80 pin connector that includes power, 
ground, and jumper signals in addition to the SCSI signal for two byte wide 
transfers. This connector has wide industry acceptance and is used in backplane 
configurations. This connector is not documented in either SCSI-2 or SCSI-3, 
only in an SFF document.

SCSI devices designed for two byte wide transfers should use either the 68 pin 
high density connector or the SCA connector. These are the connectors expected 
by customers.