Owner`s manual
Page A-7Roadrunner SCSI Bus Compatibility
A.2.1Termination Procedure (Without External Terminator)
1.All AMOS based computers (with or without Roadrunner upgrades) with
one SCSI hard disk drive must have that hard disk drive installed with its
terminators installed.
2.All AMOS based computers (with or without Roadrunner upgrades) with
more than one SCSI device must insure that only the last SCSI device, the
device attached to the connector located farthest down the cable away
from the CPU, board has its terminators installed. Any other SCSI devices
must have their terminators removed.
3.All AMOS based computers (with or without Roadrunner upgrades) which
have a SCSI magnetic tape drive as their only SCSI device must have the
tape drive configured with its terminators installed.
4.For subsystem installations used in AMOS based applications, the last
SCSI device attached to the connector located farthest down the cable
away from the host computer must have its terminators installed.
A.3TERMINATION POWER
In order to properly control SCSI bus termination, a termination power source must be
provided; this is especially important when using an external terminator.
Why is Termination Power so important when using an external terminator?
In order for terminators to do their job, they must have a power source. In most (but not
all) cases, a SCSI peripheral will supply termination power to its own on-board
terminators, even if the SCSI host controller or no other SCSI peripheral is supplying
termination power to the SCSI bus. However, for an external terminator to be effective
there has to be termination power supplied to the SCSI bus. If no termination power is
available, the external terminator is not going to do its job, which means your SCSI bus
is not terminated. This may result in a computer that either won’t boot or once booted
may tend to hang frequently. Because SCSI-2 devices transfer data at a higher rate,
they are more prone to display problems when improperly terminated.
The termination power source can be configured in one of two ways, depending on your
application:
AMOS based computers with SCSI-2 implementation (i.e., AM-4000
computers, AM-540 enhanced AM-3000M computers, all Roadrunner
enhanced computers, etc) should be configured to supply termination
power via the host controller. When termination power is supplied by the
host controller, it is not necessary to have one of your internally mounted
SCSI peripherals configured to supply termination power to the SCSI bus.
PDI-03500-50, Rev. B00