Connect multiple SCSI devices by chaining them together with
shielded 68-pin VHDCI to 68-pin HD cables. The connectors on these
cables are keyed to ensure proper pin-1 to pin-1 registration. Refer
to the peripheral manual for instructions on attaching SCSI cables.
Peripheral storage devices are normally shipped with the required
SCSI cables.
Table 2-3 “SCSI Bus Widths and Speeds” below shows the
SCSI bus widths and speeds as that have been established by the
SCSI Trade Association (STA).
Table 2-3 SCSI Bus Widths and Speeds
Type[1] | SCSI Bus Width (in Bits) | SCSI Bus Speed Maximum
Data Rate (in Mbytes/Second) |
|---|
SCSI-1 | 8 | 5 |
Fast SCSI | 8 | 10 |
Fast Wide SCSI | 16 | 20 |
Ultra SCSI | 8 | 20 |
Wide Ultra SCSI | 16 | 40 |
Ultra2 SCSI | 8 | 40 |
Wide Ultra2 SCSI | 16 | 80 |
You can connect up to eight SCSI, Fast SCSI, and Ultra SCSI
devices on a single-ended Ultra SCSI bus if they are evenly spaced
on a 1.5 m Ultra 2 SCSI cable (0.19 m between devices).
You can connect up to four devices if they are evenly spaced
on a 3 m Ultra SCSI cable (0.75 m between devices). The single-ended
SCSI bus must not exceed 3 m (total internal and external cable
lengths) even with fewer than four devices.
For Low Voltage Differential (LVD) applications, you can connect
up to 16 devices if they are evenly spaced on an Ultra SCSI cable
(0.19 m minimum between devices).
Table 2-4 “Maximum SCSI Bus Lengths” below shows the
maximum bus length for each of the SCSI types.
Table 2-4 Maximum SCSI Bus Lengths
Type | Maximum
Bus Length (in Meters)(1) | Maximum Devices |
|---|
Single-ended (SE) | Low Voltage Differential
(LVD) | High Voltage Differential
(HVD) |
|---|
SCSI-1 | 6 | 12.5 | 25 | 8 |
Fast SCSI | 3 | 12.5 | 25 | 8 |
Fast Wide SCSI | 3 | 12.5 | 25 | 16 |
Ultra SCSI | 1.5 | 12.5 | 25 | 8 |
Ultra SCSI | 3 | - | - | 4 |
Wide Ultra SCSI | - | 12.5 | 25 | 16 |
Wide Ultra SCSI | 1.5 | - | - | 8 |
Wide Ultra SCSI | 3 | - | - | 4 |
Ultra2 SCSI | (2) | 12.5 | (2) | 8 |
Wide Ultra2 SCSI | (2) | 12.5 | (2) | 16 |
(1)This
parameter can be exceeded in point-to-point and engineered applications. (2)Single-ended
and High Voltage Differential are not defined at Ultra2 speeds. |
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