The Advanced Telecom Computing Architecture (AdvancedTCA) is gathering momentum among telecom gear makers, but there are two paths to take regarding switched interconnect standards (see AdvancedTCA Makes Headway).

Two groups have come up with their own proposed standard ways to interconnect processors, memory controllers, and other in-system devices for carrier-grade networking environments. The RapidIO Trade Association (RIO) and Advanced Switching Interconnect SIG (ASI SIG) are each aiming to handle the demands of multi-gigabit backplane applications that will push the limits of tomorrow's telecom systems.

The significance of ATCA, which is based on the PCI Industrial Computer Manufacturers Group (PICMG) 3.0 group of standards, can't be overstated. The standards push seeks to assure that telecom components will become more like PC parts in that they'll be commodity items. This will result in lower overall prices for telecom equipment, because previously proprietary components will be off-the-shelf. And it will result in lower operations expenses for carriers, because ATCA gear will interoperate with other devices from different manufacturers.

But there are several speed bumps on the road to one set of standards for all telecom gear -- and the latest appears to involve different interconnection techniques.

"ATCA has become the evaluation platform of choice,” explains Dan Bouvier, PowerPC architecture manager for Freescale Semiconductor Inc. and chairman of RIO. “Every OEM’s lab has ATCA chassis in it. And that’s where they are evaluating all of the new backplane technologies, protocols, next-generation system architectures, and associated topologies” like those for RIO and ASI SIG.

Is Ethernet the answer for these connections? Not really. Ethernet was a natural fit for PICMG 3.1 as it’s pervasive, and a huge ecosystem of board and component makers, standards, and software stands behind it. But there are technical limitations to using Ethernet in high-availability communications equipment with multi-gigabit-per-second throughputs, according to OEMs, especially the computing power required to terminate the TCP/IP protocol stack in an Ethernet environment.

From that knowledge grew the two distinct approaches to a switched interconnect: RIO and ASI. ASI is now PICMG AdvancedTCA 3.4 and RIO is PICMG AdvancedTCA 3.5.

Before highlighting the two groups' differences, it helps to know what a “switched interconnect" is in the first place. Lucent Technologies Inc.'s (NYSE: LU) Dave Wickliff, who is vice chair of the RIO Steering Committee, explains the concept this way:

“In the classic PCI bus implementation, you can have up to eight boards or devices, all sitting on the same electrical bus or electrical signal path. You have a basic physical limitation in your system as to how fast you could drive that with all the different devices hanging off the same wire.

“With a switched interconnect, we say, ‘Let’s put two nodes on a wire -- a sender and receiver -- and we can drive that little wire much faster.' " Once the sender and receiver are established, Wickliff says, a switch can be used to stitch together several point-to-point links and "recreate the interconnect that you had with the bus."

All that said, in a world where packet-based applications are bringing the computing and communications worlds together, RapidIO (communications) and ASI (computing) are running a dead heat.

RapidIO was originally put forth by Freescale with an eye toward the embedded computing, real-time operating system (RTOS) world that houses Freescale’s PowerQUICC control plane CPUs and wireless base-station DSPs.

The RIO trade group comprises these same sorts of embedded players: Ericsson AB (Nasdaq: ERICY), Alcatel SA (NYSE: ALA; Paris: CGEP:PA), Texas Instruments Inc. (NYSE: TXN), Mercury Computer Systems Inc., and so on.

ASI grew from Intel Corp.'s (Nasdaq: INTC) interest in a scheme to connect PCs, servers, and storage at multi-gigabit speeds with very high availability. Today the group includes storage powerhouse EMC, Huawei Technologies Co. Ltd., and Siemens AG (NYSE: SI; Frankfurt: SIE), among many others. ASI has more silicon design engineering and semiconductor IP providers than does RIO, mainly because these folks are in the business of pleasing Intel.

The bigger goal for each group is to pull in the hundreds of other hardware and software concerns that could ensure its proposed standard's commercial success.

Who will win as these two groups advance their cause? In the short term, the programmable logic players, including companies such as Xilinx Inc. (Nasdaq: XLNX) and Altera Corp. (Nasdaq: ALTR). Until chip A can talk to chip B in the same language via an interconnect standard, equipment OEMs will turn to programmable devices to bridge them together. Engineers often call these parts “glue logic.”

So the two standards are going to coexist for a while. And, until silicon built to RapidIO and ASI appears, around mid-2005 and mid-2006 respectively, programmable logic will be continue to provide the glue that systems vendors need to meet carrier demands (see ATCA to Be Worth $3.7B in 2007). Unlike the stock market, the programmable chips market likes a little uncertainty.

— Gale Morrison, special to Light Reading