HP Surestore 80ex - Optical Jukebox, User Manual

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Appendix B B-3
Operating This Jukebox on a SCSI Bus
A Brief Overview of SCSI
Op
eration o
n
a
SC
SI
Bu
s
an ID greater than 7, would always assume it won the contention and would attempt
to talk, perhaps at the same time as a device with an ID above 7 that was contending
for the bus. The following diagram shows the priority scale of IDs when the priority
of the two blocks of eight are reversed.
The diagram below shows the linear addressing of a simple, narrow bus with the
host adapter set at a SCSI ID of 7. The device ID does not determine where the
device is physically placed on the bus.
LUN Addressing
This jukebox does not support logical unit numbering (LUN) addressing.
Transfer Rates on the Bus
Initially, the SCSI specification defined a 5 MB/s synchronous data transfer rate on
the narrow bus. SCSI now also defines "Fast" which is 10 MB/s on a narrow bus and
20 MB/s on a wide bus. Another definition is "Ultra," also known as "Fast-20"
which is 20 MB/s transfer rate on a narrow bus and 40 MB/s on a wide bus.
8 9 10 11 12 13 14 15 0 1 2 3 4 5 6 7
Wide Address Range
Narrow
Addresses
Priority