28
AP7500 Hardware Reference Guide
II.
Components
Ultra2 SCSI Disk Drive
The Ultra2 SCSI disk drive has separate signal and power connections. The
power connector is the same as standard hard disk drive power. The signal
cable is different. For proper signal stability in Ultra2 speeds, a special twisted
ribbon cable must be used. Each pair of wires are twisted for signal shield-
ing like that of high speed (e.g. category 5) LAN cabling.
II. System Components
External Ultra2 SCSI Terminator
To prevent SCSI signal loss, the provided exter-
nal SCSI terminator must be used at the end of the
68-pin SCSI cable. 50-pin SCSI cables may also
use terminators but usually use termination jump-
ers on the device itself. Currently Wide-SCSI de-
vices have termination jumpers but Ultra2 devices
do not. Some manufacturers ship SCSI devices
with the terminator set, others do not. All termi-
nation jumpers must be removed along the cable
where the external SCSI terminator is used.
IMPORTANT: You must use Ultra2 SCSI ribbon cables for Ultra2 devices.
Ultra2 ribbon cables (may be colored red and white) are similar to wide-
SCSI ribbon cables (normally colored gray) but each pair of wire is twisted
to reduce signal interference.
Ultra2 SCSI hard disk drive connections
Red stripe of signal cable
Red stripe of power cable
Ultra2
SCSI
Drive