C-4 Appendix C
HotSwap Disk Bay (D Class Only)
• The delay spin feature causes the spin-up to delay for a time approximately equal to
ten times the SCSI address selected for a given drive in seconds. Delay spin can be
overridden if the software attempts to access a disk drive before it has timed out and
begun its spin up. The disk in the top position will spin-up as soon as power is
applied.
• The remote spin feature gives the controlling software complete control over the disk
drive spindle motor. Software can accordingly issue appropriate SCSI commands to
spin-up or spin-down on the drive. The current HP UNIX software does not support
this feature; therefore, it is hard disabled at the HotSwap backplane.
• The module detect lines are four connector pins of two different lengths. All four pins
are tied to circuit ground in the disk module. The backplane can detect the presence
or absence of the connections and cause SCSI resets when a disk module is removed
or replaced.
• The power valid line indicates that the DC voltages to the disk module are
satisfactory for proper operation. This feature is not supported in this systems
implementation but will be used in the external products.
The module addresses are hard wired for each position in the HotSwap module. A switch
position on the backplane selects one of 2 address ranges. (This will be described later)
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