What is LVD (Low Voltage Differential)?
Low Voltage Differential is a new hardware bus driver type for SCSI-3. It first becomes important with Fast-40 (Ultra2) devices. If single ended (S.E.) bus drivers were used with Fast-40, the bus length would be limited to about .75 meters! Since this was clearly un-acceptable, and the older High Voltage Differential (HVD) interface adds too much cost to a system, ANSI defined a new form of differential interface that is less expensive to implement because the bus driver logic dissipates little enough power that it can be included in LSI chips. They also wanted to make sure they avoided the confusion caused by HVD (HVD and S.E. devices cannot co-exist on a bus), so they specified that if an LVD device is designed properly, it can switch to S.E. mode and operate with S.E. devices on the same bus segment. Another difference worth noting is that LVD devices do not contain on-board terminators. You need to attach an LVD terminator to the end of the cable instead of using a device to termin
