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Chapter 2. Backplane Architecture
The 8260 backplane consists of the following two buses:
•
Enhanced TriChannel
•
ShuntBus
These two buses are standard features of all the 8260 models and are installed
on every 8260 shipped to the customers.
The following sections provide detailed information about the 8260 backplane
and how the backplane buses operate.
2.1 LAN Segments on the Backplane
On each backplane bus (both Enhanced TriChannel and ShuntBus) there are 96
pins
which are used for passing the network traffic between the media modules
installed in the hub as well as the control signals between the media modules,
fault-tolerant Controller module, and Distributed Management Module (DMM).
The control signals are used to carry clocking, voltage, status and other
information pertinent to the proper operation of the hub and the installed
modules.
On the Enhanced TriChannel, 54 pins are available to be used for passing
network traffic. the rest of the pins are used for non-data traffic signals. These
signals are used for passing control signals between the Controller module and
the media modules as well as signals between the Management module and the
media modules. More information about these non-data traffic signals are
provided in 2.5.1, “Management Buses” on page 26.
On the Enhanced TriChannel, the pins used for passing the network traffic are
not permanently allocated to a specific type of network. Instead a pin may be
configured to be used for passing either token-ring, Ethernet or FDDI packets at
any one time. This enables more efficient utilization of the backplane resources.
The following is the maximum number of permitted LAN segments when a single
protocol is used on the Enhanced TriChannel:
•
6 Ethernet segments or
•
7 token-ring segments or
•
4 FDDI segments
Note that you are allowed to have a mixture of token-ring, Ethernet and FDDI
segments on the Enhanced TriChannel. In this case, the exact number of each
network type which is allowed in a mixed protocol environment depends on the
configuration of your hub. For detailed information about the permitted
configurations in a mixed protocol environment please refer to 2.5, “Network
Allocations on the 8260 Backplane” on page 23.
Figure 3 on page 14 provides an overview of the Enhanced TriChannel bus.
Copyright IBM Corp. 1995 13