Compaq EK-SMCPO-UG. C01 manual Differential/Wide UltraSCSI Bus, Replacing the UPS

Maintenance 3-13

Replacing the UPS

Proceed as follows to replace the UPS:

1.Ensure the UPS power switch is set to off.

2.Disconnect the pedestal power cord from the UPS.

3.Disconnect the UPS power cord from the wall outlet.

4.Disconnect the signal control cable from the UPS

5.Install the replacement UPS and reconnect the power cords and the signal control cable.

6.Set the UPS power switch to “on” and then power up the pedestal.

Differential/Wide UltraSCSI Bus

The reliability of data transfers on a SCSI bus depends on the following factors:

■The bus transmission rate

■The maximum SCSI bus length (a function of bus type, the transmission rate, and the use of SCSI bus converters)

■The total length of the SCSI bus (as measured from the host bus terminator to the subsystem terminator)

■MT/s (mega-transfers per second) is the repetitive rate at which words of data are transferred across a bus. The number of megabytes per second (Mb/s) is determined by the bus width (8 or 16-bit) and the number of bytes per word (1 or 2, respectively)

Table 3–2 lists the maximum SCSI bus lengths and the longest SCSI cables recommended by Compaq.

NOTE: Because the bus length includes the cable plus the backplane distance inside the enclosure, the recommended maximum cable lengths listed are not the same as the maximum bus length.