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CHAPTER 4: Operation
4.1 Overview
The SCSI Fiber Optic Extender converts SCSI data and command
information into a serial data stream that’s transmitted over a high-speed
(175-Mhz) fiberoptic interface to the remote Extender. The remote unit
decodes the data stream and reconverts it back into proper SCSI signals.
The fiberoptic serial link conforms to the ANSI X3T9.5 encoding scheme
specified in FDDI local area networks and is virtually immune to all forms
of radio-frequency and electromagnetic interferences (RFI/EMI). An
unauthorized tap of the link is nearly impossible without detection.
4.2 System Performance
The SCSI Fiber Optic Extender will support any combination of
asynchronous and synchronous SCSI devices on the bus. Overall system
performance will depend on the individual data rate and protocol of each
SCSI device plus the overhead of the host computer.
In general, devices connected via a SCSI Fiber Optic Extender link up to
300 feet ( about 100 m) will achieve aggregate data rates of 225 kilobytes
per second in asynchronous mode. In synchronous mode, with a byte offset
of 8, sustainable data rates of 4 megabytes per second can be expected. A
synchronous offset of 16 will provide 5 megabytes per second data rates.
4.3 System Configuration Options
The SCSI Fiber Optic Extender supports a maximum data rate of 10
megabytes per second. This data rate is often referred to as Fast SCSI. To
ensure optimum system performance, some system configurations may
require a secondary SCSI channel to interface with the Extender (see
Figure
4-1
).
4. Operation
