Embedded Computing Design - OpenSystems Media

The current landscape
of
switch fabrics
and RapidIO
As system
designers strive for higher
levels of speed, bandwidth, and performance in
embedded systems, traditional intrasystem interconnect structures
based on hierarchical buses have begun to fall short in their ability to provide
the necessary functions. Despite the application of novel techniques to further
exploit bus-based approaches, the resulting complexity and need to balance
competing design issues have limited their broad applicability.
The increasing use of high-bandwidth smart peripherals, as well as the advantages
of direct communications between various system devices and elements,
has brought bus-based interconnect technologies under further scrutiny.
To combat the inadequacies of traditional interconnect structures that have risen
from the modern requirements of embedded system designers, several switch
fabric technologies have come into play – each vying for its own foothold in
the market.
Although there are over 60 switch fabrics currently documented, with several
more anticipated to show up on the scene, there are only a few that utilize an
open architecture platform, thereby making them available to the broadest
number of users and increasing their chances of utilization in the marketplace.
Here, we’ll examine some of the most widely adopted open architecture fabrics
to provide an overview and comparison of each, then we’ll focus on some recent
developments to RapidIO, one of the leading open architecture switch fabrics.
By Luc Torres
The Ethernet legacy
Because Ethernet is one of the original
switch fabric technologies, it stands to
reason that it is one of the most widely
used. However, because of Ethernet’s
slower performance, its use has been
primarily in the field of industrial control
and medical imaging. Faster versions
of Ethernet, both gigabit and 10-gigabit
versions, are in development and will help
expand its use in different applications.
However, Ethernet commands a significant
amount of a system’s processor load, since
it mandates that data be shared when a
series of I/O packets are sent. This decreases
some system functionality, since
much of the processor’s capacity is used
to transfer the data packets.
The InfiniBand factor
The InfiniBand Trade Association
(www.infinibandta.org), a membersupported
organization that heads the
development of the InfiniBand protocol,
defines the architecture as a unified
fabric that takes I/O outside of the
box and provides a mechanism to share
I/O interconnects among many servers.
Embedded Computing Design Summer 2004 / 25