Seagate ST118202LW/LC manual Single-ended and low voltage differential modes, Scsi ID jumpers

20 Cheetah 18 Installation Guide, Rev. A

Single-ended and low voltage differential modes

This drive incorporates two different transceivers to allow you to use it in traditional systems which may use single-ended (SE) drivers and receivers, or to use it in low voltage differential (LVD) capable systems which use LVD drivers and receivers.

You can configure the drive to switch between SE and LVD modes automatically or force it to operate in SE mode only as described later in this guide.

LVD technology enhances parallel SCSI I/O performance, reduces power consumption, increases allowable cable lengths, and improves device connectivity beyond SE capabilities.

Note. To operate at the Ultra2 SCSI rates in LVD mode, all devices on the same bus must be running in LVD mode. If you add any single-ended device to a bus that is operat- ing in LVD mode, all devices drop back to operating in single-ended mode. This eliminates the possibility of reaching Ultra2 SCSI transfer rates.

Warning. Do not mix LVD drives on the same daisy chain with devices having high voltage differential (HVD) inter- face circuits.

SCSI ID jumpers

Each device on the SCSI chain must have a unique SCSI ID. The host system’s SCSI controller usually uses the ID that has the highest priority interrupt in the SCSI I/O system. This is always ID7. ID0 has the lowest priority in an 8-bit I/O system. ID8 has the lowest priority in a 16-bit I/O system. The lower priority SCSI IDs are normally used for other SCSI devices such as this Cheetah disc drive.