Adding External Scsi Peripheral Devices; Scsi Cable Lengths And Device Speeds - Intergraph StudioZ GT RAX System Reference Manual

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Adding External SCSI Peripheral Devices

The system features integrated Narrow Ultra SCSI and Wide Ultra2 SCSI controllers. However,
only the Narrow Ultra SCSI controller has an external port. You can connect external single-
ended Narrow Ultra SCSI peripheral devices to this port. To connect external Wide Ultra or Wide
Ultra2 peripheral devices, you must install the appropriate SCSI controller as an expansion card.
NOTE Most SCSI controllers do not recognize a hard disk drive that was formatted using a
different brand of controller. For example, a hard disk drive formatted with an
Adaptec SCSI controller will not work with a Symbios SCSI controller. You must use
only Symbios-formatted hard disk drives with a Symbios SCSI controller.

SCSI Cable Lengths and Device Speeds

For each SCSI bus, the type of bus and the data clock speed of the fastest device on that bus
determine its maximum length. Knowing this, you can determine the maximum cable length you
can use to connect external SCSI devices to the system.
The following table provides a guide to maximum SCSI bus length. Note that bus width (for
example, Narrow versus Wide) does not affect the maximum bus length.
Speed of the fastest
device on the bus
5 MHz (SCSI-1)
10 MHz (SCSI-2 or Fast)
20 MHz (Ultra or Fast20)
40 MHz (Ultra2 or Fast40)
The total cable length on the system's Narrow Ultra SCSI bus is the sum of the following:
Narrow Ultra SCSI cable in the system 56 inches (1.4 meters)
SCSI cable inside each internal device connected to the Narrow Ultra SCSI cable typically 8
inches (0.2 meters) or less
SCSI cable between the system and the first external device
SCSI cable between each external device
Note that the maximum speed of a SCSI bus is limited to the speed of the slowest device on that
bus.
Single-ended bus Differential bus
19.7 ft / 6 m 82 ft / 25 m
9.8 ft / 3 m 82 ft / 25 m
4.9 ft / 1.5 m 39.4 ft / 12 m
Not recommended Not specified
Low-voltage
differential bus
39.4 ft / 12 m
39.4 ft / 12 m
39.4 ft / 12 m
39.4 ft / 12 m