First Virtual Communications 3000 user manual Components, Devices, Length in Metres Transfer Speed

Installation and Setup

Note Ultra SCSI has very stringent requirements regarding cable length. Any cables connected to Ultra devices must conform to Ultra SCSI specifications. When there are excess of 4 devices cable length should be no greater than 1.8 metres for single ended Ultra SCSI. The implication of this

is that for any Ultra SCSI system the initiator and target will try to transfer data at Ultra SCSI rates during the initialisation process regardless of the number of devices and cable length. When Ultra SCSI cable length restrictions can be violated (in the case of buses with more than 4 devices) the transfer rate must be reduced at the initiator side.

Table 2-2 Cable Lengths Vs Transfer Rates

Length in Metres	Transfer Speed
6 Metres	5 MHz (10 MB/S for wide (16 bit) SCSI-2, 5MB/S for narrow SCSI-2)
3 Metres	10	MHz (20 MB/S for wide (16 bit) SCSI-2, 10MB/S for narrow SCSI-2)
3 Metres	20	MHz (4 devices or less) Ultra SCSI single ended
1.8 Metres	20	MHz (greater than 4 devices) Ultra SCSI single ended
25 Metres	SCSI-2 Differential mode

Components

Power Supplies

The Power Supplies are housed in removal canisters and are supplied as such. To replace a power supply simply press the button as shown in Figure 2-9 and withdraw the carrier. The PSU is hot pluggable7. Refer to the heading on page 2-14 for more details.

Figure 2-9 Removal and insertion of a Power Supply Unit

Note: The Power Supplies are not Auto Sensing and there are two different types depending on the AC Input. Power Supplies for the US market are clearly marked with a label stating 115V.

Devices

Devices are housed in two types of canisters. The top LED in the device carrier indicates SCSI activity on the device and is green. The bottom LED is red and indicates a fault condition.8 A front view of the device carrier is shown in Figure 2-10.

Figure 2-10 Device carrier

7To allow correct functionality of the power supply circuitry, please ensure that at least one minute has elapsed between removal and re-insertion of the power supply unit.

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