DEC AlphaServer 2100, Owner'S Manual

Page: 123 / 192

SCSI Buses
SCSI Buses
A PCI-based SCSI controller provides a single-ended SCSI bus
for the system. There is a SCSI bus expansion port on the rear
of the system for extending the bus outside the system.
All tabletop or rackmounted SCSI-2 devices are supported via
EISA- or PCI-based SCSI adapters. Use the following rules to
determine if a device can be used on your system:
• The device must be supported by the operating system.
Consult the software product description or hardware vendor.
• No more than seven devices can be on any one SCSI-2
controller, and each must have a unique SCSI ID.
• The entire SCSI bus length, from terminator to terminator,
must not exceed 6 meters for single-ended SCSI-2 at 5
MB/sec, or 3 meters for single-ended SCSI-2 at 10 MB/sec.
For AlphaServer 2100 pedestal enclosures, the internal
cabling for the removable media bus is 2.5 meters; therefore
the maximum length for external expansion is 3.5 meters.
Note
If you extend the SCSI bus into the internal
StorageWorks shelf, you cannot expand the bus
externally.
Internal SCSI
Bus
The Fast SCSI-2 adapter on the standard I/O module supports
the internal removable-media devices:
• Up to three 5.25-in. half-height devices
or
• One 5.25-in. full-height device and one 5.25-in. half-height
device
This bus can be extended to a StorageWorks shelf or an external
expander to support up to seven drives.
Options and Upgrades 3–39