the Engineers' Guide to VME, VPX & VXS 2013 - Subscribe

SPECIAL FEATURE
We are also in the process or creating one or more “dot” specifications
to cover the use of alternate connectors (optical, RF, etc). We decided
that these alternate connectors were best defined in a dot(s) spec
rather than adding them to the current VITA 65 spec. New profiles
that use only the VITA 46 (VPX) connector will continue to be added
to VITA 65.
EECatalog: Conventional wisdom says boards are getting hotter.
What are you seeing, and what are the trends in thermal management?
Patterson, Aitech: “Conventional wisdom” only applies when one
complies and acquiesces to convention, when in fact, only some
boards are getting hotter. Newer processor technologies—like Freescale’s
QorIQ and ARM processors— are challenging convention in
terms of performance and power dissipation. The proof can be seen
in today’s full-featured 3G and 4G Smartphones that provide stellar
performance with milliwatt power dissipations. Reductions in SWaP
remain the goal, the engineering prize and the promise of Nirvana.
Edwards, Curtiss-Wright: Boards are getting hotter … and cooler.
Certainly at the high end we are seeing boards getting hotter. This is
driven primarily by the latest generation Intel processors, GPGPUs
and large FPGAs. But we are also seeing that a number of products
(especially in 3U) are using lower power devices such as lower-end
Power Architecture and ARM processors. These processors have more
performance with less power than the CPUs they are replacing from
5+ years ago.
Slonosky, Curtiss-Wright: For technology insertions or technology
refreshes (and there is a difference), customers are requiring next
generation products to fit into the same or similar thermal footprint.
Hence, to meet these needs COTS vendors are designing next generation
boards that provide similar thermal footprints to those in older
products but with increased performance. Not all next-generation
products are going to be able to “fit” thermally—but many can be.
On the hot end there are a number of innovative approaches that
companies are taking for thermal management. Air Flow Through or
AFT (VITA 48.5) is becoming more popular for higher power products.
Curtiss-Wright also has a patent pending approach to cooling
high power Intel processors.
EECatalog: The march towards SFFs has affected even predominantly
“U” based VITA. Why is the market so interested in small
form factors?
Patterson, Aitech: Small, rugged, stand-alone form factors, coupled
with high performance, power-efficient, deeply embedded processors
bring the reality of distributed processing and “computing-at-theedge”
to today’s mobile computing platforms and vehicles. Bus-based
embedded computing subsystems are ideal and still used to create
large, centralized embedded computers.
Compact “smaller than U” embedded computers acting as remote
interface units or data concentrators can now be distributed at the
end of high speed networks and communication buses to gather,
analyze and—more importantly— can gather and compress sensor
data closer to the sensor, then send that data to the central mission
computer, which in-turn, lowers the overall network bandwidth.
Edwards, Curtiss-Wright: In a word: “SWaP”. SFF boards fit best
in niches where the platform is constrained in Size, Weight and/or
Power. Typically smaller UAVs and some ground systems are the biggest
areas in defense for SFF. Systems that need more performance
use 3U or 6U since they can be used to build the larger systems
required by more demanding applications.
EECatalog: Talk a bit about inter- and intra-box interconnects.
What’s the state of the art today, and where does the user base want
us to go?
Patterson, Aitech: Currently, inter-box interconnect is tending to
adopt the Ethernet TCP/IP and UDP protocols almost universally.
The advent of multi-Gigahertz, multi-core processors with higher
speed RAM and block-oriented Flash memory allows the system
designer to easily overwhelm the box-to-box communications protocol
stacks with plenty of speed and data throughputs left over for
analysis and compression algorithms.
Intra-box data passing is adopting the asynchronous high speed PCIe
(PCI Express) and SRIO (Serial Rapid I/O) serial fabrics with synchronous,
even-driven parallel, data buses (like VME and cPCI) that
are providing the real time, interrupt-based system synchronization.
A parallel bus’ interrupt-driven structure with minimal latencies is
the only architecture that can handle these kinds of control-loop
applications in real-time.
Serial fabrics cannot yet replace parallel buses in these closed-loop
feedback systems: none of these fabrics possess the needed real-time
synchronization capability. This is why many systems integrators
for event-driven apps are choosing a hybrid approach to systems
designs—mixing the power, performance and raw speed of high
speed serial data pipes and parallel buses like VME or cPCI for the
control loops.
Edwards, Curtiss-Wright: Today users are predominantly using
3.125 – 6.25 Gbaud fabrics such as SRIO Gen 1 or 2, 10 GigE or PCIe
Gen 1 or 2 inside a box. Interconnects are generally copper. Connection
between boxes are less standardized. We see customers using
sFPDP, Fibre Channel, 10 GigE and proprietary interfaces. Optical
and copper are both used for box-to-box.
40 GigE data plane and PCIe Gen 3 expansion plane products will
be available in the next year. Optical and RF user I/O modules will
also become more prevalent. The general feeling is that VPX can, with
proper layout/routing, support 10Gbaud signaling. Beyond that, the
general belief is that we need to move to optical interfaces (or pick a
new connector that supports 20-25 Gbaud signaling).
EECatalog: Board consolidation continues unabated, and it’s looking
today like that could wind up being all manner of svelte, purposebuilt
boxes that don’t seem to follow any standard at all (let alone
VME or VPX). What’s up with this trend?
8 Engineers’ Guide to VME, VPX & VXS 2013