SCSI | Small Computer System |
| command set that enables computers and peripherals to communicate with each |
| other. HP’s Ultrium drives adhere to the SCSI specifications (see Chapter 1, |
| “Interface Implementation” in Volume 3, The SCSI Interface, of the HP Ultrium |
| Technical Reference Manual) and support all features required by those standard. |
| |
| These terms define how the signals are transmitted along the cable. |
| With |
| signal's value is determined by comparing the signal to a paired ground wire. |
| Signal quality tends to decrease over longer cable lengths or at increased signal |
| speed. |
| With low voltage differential (LVD) signaling, signals travel along two wires and |
| the difference in voltage between the wire pairs determines the signal value. This |
| enables faster data rates and longer cabling with less susceptibility to noise than |
| SE signaling and reduced power consumption. |
| Narrow and Wide, Fast, Ultra SCSI and above |
| Narrow SCSI devices can transfer data one byte |
| called |
| protocols. They have a |
| Wide SCSI devices can transfer two bytes of data simultaneously |
| They usually have a single, |
| arrangement is part of the |
| |
| the same bus without problem, provided certain rules are followed. |
| Fast SCSI can transfer data at up to 20 MB/s wide, using a cable of up to 6 |
| meters total length. |
| Ultra SCSI can transfer data at up to 40 MB/s wide, but the cable length cannot |
| exceed 3 meters (it is also known as “Fast20”). |
| Ultra2 SCSI can transfer data at up to 80 MB/s wide, using a cable of up to 25 |
| meters total length for a single device, or up to 12 meters for two or more devices |
| (it is also known as “Fast40”). |
| Ultra3 or Ultra160 can transfer data at up to 160 MB/s wide. Cable lengths are |
| as for Ultra2. |
| Ultra4 or Ultra320 transfer data at up to 320 MB/s. Cable lengths are as for |
| Ultra2. |
Glossary
Glossary 189