17
How cascade connections operate
The method for cascading MC5 units is straightforward and
requires no hardware settings or lengthy configuration process.
This is due to the
Port Direct
communication system that allows
them to locate each other and share information.
The method of linking MC5 units is the same regardless of the
cascade level, or number of devices attached. Put simply:
•
A single cascade link is made by connecting a
COMPUTER
CONNECTIONS
socket of one unit to a
CATx USER PORTS
socket of the unit below it.
Such a single link would allow just one user from the higher MC5
unit to access any of the computer systems attached to the lower
one. However, a single link can cause a bottleneck for multi-user
systems and cause port numbering problems, so the minimum
permissible group link between MC5 units is a triple (quad cascade
links are recommended). These allow three or four users to
simultaneously access computer systems situated anywhere within
the cascade tree.
When triple or quad cascade links are made between units,
each MC5 will automatically recognise the links and treat them
accordingly. The links within a triple or quad group will then be
allocated to users according to their general availability in that
group, not as specific individual lines. To do this, each link group
has an access number, which is determined by the ports to which
they are connected on the switch.
For instance, a quad group connected to computer ports 1, 2, 3
and 4 of an MC5 unit would always be known as 41, the next
quad group connected to ports 5 to 8 would always carry the
number 42, and so on. The diagram here summarises the ports to
which triple and quad groups must be connected and the resulting
group numbers attained in the positions here
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The central purpose of the link group system is that each user can
use a unique address to locate a particular computer. However, as
with the Internet, the route to get there could be slightly different
each time. This avoids any route blocking that could easily be
caused by other users occupying any specific link lines.
Note: Triple and quad link groups may be mixed on one unit
providing the differing link groups lie within appropriate port
boundaries shown opposite - see
Tips for successful cascading
for more details.
Port boundaries and numbering for triple link groups
(sixteen port models use groups 31 to 35 only)
Port boundaries and numbering for quad link groups
(sixteen port models use groups 41 to 44 only)
See also
•
Addressing computers in a cascade
•
Connecting MC5 units in cascade
•
Testing specific links to cascaded computers
