The ATCA (Advanced Telecommunications Computing Architecture) and smaller-form-factor µTCA (MicroTCA) standards (collectively referred to as xTCA) for blade-based systems are increasingly popular in applications including telecommunications, military, and industrial automation. Embedded teams have a number of options for connecting multiple processors across xTCA backplanes and that choice can have a significant impact on realized system performance. PCI Express (PCIe) is often the best choice for maximum performance in multiprocessor systems. Moreover, Intel® Architecture (IA) processors natively support PCIe affording both flexibility and optimum performance in xTCA-based systems.
The ATCA and µTCA standards are promulgated by the PICMG organization that focuses on modular computing technology standards. Both were conceived as ruggedized platforms that allowed teams to build reliable, mission-critical systems based on standard products including backplanes, chassis, and the boards referred to as blades that carry the system functionality.
All xTCA systems also support the use of AMC (Advanced Mezzanine Card) modules that are typically used to implement the microprocessor and support chip complex. AMC cards are added to ATCA blades via a mezzanine connector as the name implies. In the case of µTCA, the AMC cards can be inserted directly into the backplane.
The xTCA specifications don’t specify the manner in which blade-to-blade or module-to-module communications are carried out. Instead the specifications allow the design team to choose the best approach by allowing Ethernet, Infiniband, RapidIO, and other choices along with PCIe.
Ethernet has been a popular choice as an xTCA interconnect fabric because of inherent software support. But Ethernet lacks the bandwidth of PCIe. Infiniband has been successfully used in storage-centric systems, but it lacks the flexibility of PCIe. Indeed design teams are finding that PCIe is the best choice in multiprocessor-based systems.
General Electric Intelligent Platforms* (GE) is one modular product vendor that is a proponent of PCIe in xTCA systems. The company has published two whitepapers on PCIe and xTCA. In “Implementing PCI Express interconnects in xTCA,” the company lists low latency, high data throughput, low CPU utilization, low implementation cost, and low power consumption as advantages of PCIe over Ethernet and Infiniband. The paper details typical architectures that might be used in industrial and medical systems (see block diagram below).
The second paper, “Designing multiple PCI Express processor nodes into xTCA host systems,” looks more deeply at how AMC technology has evolved to support multiple processors. The paper discusses how system designers can deploy multiple processors both as xTCA root complexes (masters) and end nodes. Moreover it covers the breadth of systems that use a dedicated PCIe switch to AMC modules that can essentially implement the switching function via port bifurcation when the system only requires three or four processor nodes.
GE supports PCIe in xTCA designs with products such as the Telum ASLP11 and ASLE11 AMC modules. The modules are based on Intel® Core™ 2 Duo processors and include as much as 4 Gbytes of DRAM along with AMC.2 (Gbit Ethernet) and AMC.3 (SATA interfaces). The designs can be used in a system with a PCIe switch. Alternatively the designs support PCIe port bifurcation allowing one master node to partition and group the 8 PCI lanes into four pairs with each connecting a processor on additional end-node modules.
Emerson Network Power Embedded Computing** also has a broad spectrum of xTCA and AMC modular products including the AdvancedMC Storage Modules that can act as carriers for rotating or solid-state hard drives. The company also offers the PrAMC-7211 module that integrates a Core 2 Duo processor and 2 Gbytes of memory.
Of course a system design also requires chassis and backplane components. Elma Electronic has a broad line of such products across many modular computing standards. The company web site allows you to quickly navigate to system platform and backplane pages for both µTCA and ATCA systems.
You might also be interested in modular alternatives to xTCA that also compete in the same communication, military, and industrial segments. Kenton Williston recently compared ATCA with the VPX standard that has a VMEbus heritage.
Please share you experience using a PCIe fabric as the basis for a high-performance system. Your insight would be greatly appreciated by fellow followers of the Intel® Embedded Community regardless of which xTCA or other modular standard that you experience comes from. Did you use a dedicated switch? Have you relied on port bifurcation? Contribute to the discussion via our comment facility.
Roving Reporter (Intel Contractor)
Intel® Embedded Alliance
* General Electric Intelligent Platforms is an Associate member of the Intel® Embedded Alliance
** Emerson Network Power Embedded Computing is a Premier Member of the Alliance