| The term passive means no active componants, ie no silicon. My
understanding is that the DEChub 900 backplane is simply etchs on a pcb
and therefore passive. The switching is accomplished elsewhere and at
this moment in time is a loose term to describe the s/w switching
capabilities of placing modules onto different channels. When the
dechub 900 supports ATM the switching will be done within a module and
not on the backplane, rather across the backplane.
The GIGAswitch would be an example of an 'active' backplane as it
utilises a silicon based 'crossbar' switching technology.
regs
ross
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I think that in general the DEChub 900 would be considered to
have a passive backplane. However, to be technically correct, the
management "bus" is star wired etch to the Hub Manager card, which
has a gate array for traffic control.
We claim that this arrangement is more reliable, since a module
failure in one slot cannot affect any other slot's management.
However, the Hub Manager itself is still a single point of
management failure. Similarly, in the 90, the Bus Master module is
a single point of management failure.
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| > The GIGAswitch would be an example of an 'active' backplane as it
> utilises a silicon based 'crossbar' switching technology.
Not true. GIGAswitch (and the future ATM switch) have passive backplanes,
into which you plug the switching logic. For GIGAswitch, the crossbar
logic is on a card inserted through the front. For ATM switches (not
DEChub 900), the crossbar logic might be installed through the back.
Once you get past the "passive backplane" question, then say whether
your switch is based on a bus, on a ring, or on a space switch.
A crossbar switch is one form of space switch.
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