RTC Magazine

As FPGAs increase performance in denser packages, they can fit into smaller PCBs and platforms. The latest COTS platforms are meeting these trends—with room for the future. The latest breed of FPGAs from companies like Xilinx and Altera offer very high processing performance, and designers can take advantage of their efficiency and customization for applications such as sensor data acquisition and processing, image processing, or communications. 

Military/Aerospace/Government designers who are developing with FPGA-based applications have many choices to consider, and one important aspect is the platform. Features to consider include low-profile, high-density, high-power and high-speed I/O, rear I/O flexibility and cost-effective pricing. The latest AdvancedMC (AMC) modules and MicroTCA platforms dovetail nicely with these requirements, and now is the best time to take advantage of these COTS platforms. Advanced physics organizations worldwide are adopting AMCs and MicroTCA for the next generation of systems for particle acceleration and detection experiments; this includes modules for sensor I/O, ADC/DAC, FPGA processing for stream encoding/decoding and triggers, precision timing and interlocks. These organizations were very instrumental in defining the MicroTCA.4 specification to meet high-speed data rates, high-performance processing, flexible and high-performance rear I/O options, and comprehensive platform management in a cost-effective platform.

FPGAs enable rapid product development and can be reprogrammed or reconfigured, allowing them to be updated quickly. These devices can run complex algorithms to offload processors, or to run dedicated functions. Because of their parallel architecture, they can run very efficient hardware algorithms, with speed increase of 10x to 100x over other processors. The latest generation of IEEE1394 cameras can produce image data at well over 1 Gbyte/s. High bandwidth and fast synchronization are key requirements to support these higher levels of sensor data, larger digital images, large databases and data/video/voice communications. For these types of applications, MicroTCA systems with very high-speed switching, such as PCI Express Gen 2 and Gen 3, 10GbE or 40GbE, can use a mix of AMC modules. Examples include those with FPGA and/or DSP functionality, graphical processing units (GPUs) with OpenGL for graphic-intensive computing applications, general purpose processors and storage with solid state drives.

In the past, many mil/aero designers have relied on VME. Thus, it is very natural for designers to consider VPX as the natural successor, especially since VPX was designed specifically for mil/aero applications. However, as current defense initiatives (such as the Global Information Grid) focus on a connected battlefield, the needs for mil/aero are converging with telecommunications requirements (Figure 1). ATCA and MicroTCA, which have been widely adopted for telecommunication-based applications, are making their way into defense and government applications. VPX is fine when highly rugged features are needed, but there is a hefty price to pay for its architecture. Thus, now is the best time for mil/aero designers who are developing FPGA-based designs to consider xTCA platforms. Let’s review why Micro-TCA may be better suited than ATCA.

The latest generations of FPGAs, such as the Xilinx Virtex-7, offer 2 million logic cells, which is up from 760,000 cells on the Virtex-6. They reduce bill of materials costs by up to 50 percent and reduce power consumption by as much as 70 percent. Xilinx rates the Virtex-7 as having DSP performance of 5,335 GMACs compared to 2,419 GMACs for the Virtex-6. As the performance increases in smaller and smaller packages, the PCBs they reside in can also be smaller. 

The ATCA blade form factor has a very large footprint with a 322 mm x 280 mm dimension, and can either be too big for deployment or too costly—especially when you consider including spares at each deployed location. Conversely, the first generations of MicroTCA platforms were sometimes too small, had limited power and no rear transition modules (RTMs), which created barriers for FPGA-based designs. However, the new MicroTCA.4 platforms support double-wide AMCs at 148.8 mm x 181.5 mm and up to 160W per slot of power, 10GbE or 40GbE of bandwidth and RTMs for each payload slot. These new breeds of MicroTCA platforms can be considered a standards-based “hybrid” between ATCA and MicroTCA that is sized appropriately for many FPGA-based applications today and for the future. And these AMCs can handle up to four Virtex-7 FPGA devices. Secondly, the new RTM option for AMCs has been defined to be similar in size to the mating AMC board, so there is plenty of room for additional functionality— either more FPGA processing, DSPs, or other I/O to the rear. See Table 1 and Figure 2 for comparisons.

Figure 2
The surface area of MicroTCA.4 payload boards compared to ATCA.

Table 1
Comparing MicroTCA, ATCA and VPX.

Upping the Power Density and More

As ATCA systems update their power-per-board to 350W, the power density for both the front board and RTM is about 2W per square inch. Note, however, that some of the real estate on the ATCA board is dedicated to power conversion. An AMC and RTM mated pair with 160 watts of power in a Monterey 8000 system equates to a power density of 1.9W per square inch. The AMC and MicroTCA.4 features that make it a great fit for FPGA designs include:

Low Profile Form Factor: An 8U platform provides 12 double-wide AMC payload slots with a complete and redundant infrastructure; power supplies, cooling, high-speed fabric switches, and platform management.  

Commercial Off-the-Shelf FPGA AMCs: A wide range of single width FPGA and DSP AMCs are already available in the market, such as the CommAgility AMC-V6 and AMC-2C6678. With the advent of MicroTCA.4 systems, vendors can now update these to provide larger, more powerful AMCs more suited to demanding applications. 

High-Speed Fabrics: MicroTCA platforms support up to 8 lanes of PCI Express Gen3 or up to 10GbE today, and the Monterey 8000 backplane is 40GbE-ready to future-proof next generation designs.

Rear Transition Module Flexibility: The MicroTCA.4 specification adds MicroTCA Rear Transition Modules (µRTM) for all AMC payload, and MicroTCA Carrier Hub (MCH) provides fabric switches and platform management. These µRTMs are the same dimension (148.8 mm x 181.5 mm) as an AMC so they provide plenty of room for adding highly functional components. The Monterey 8000 delivers up to 40W of power to these µRTMs. The significance is that µRTMs can be designed with a high level of functionality, such as a programmable GPU, ADC/DAC, DSP, or any high-speed I/O. The µRTMs are directly mated with their host AMC card to maximize I/O data rates.

Multiple Storage Options: Depending on your application’s storage needs, there are several options to consider. For local databases, the AMC’s interconnect can connect up to two storage AMC modules via the backplane. The AMC can also connect to a µRTM that can hold up to two SATA drives. Finally, an external NAS can be used with up to 10GbE links directly from each AMC module or from the MCH uplinks.

High Power Density: Extended power options in some MicroTCA platforms can deliver up to 160W of power per each AMC/RTM mated pair. The cooling in the platform is set up to support 120W to the AMC and 40W to the RTM. This extended power architecture does not break any standard; AMCs designed to take advantage of the extended power connector can obtain the additional 80W of power, and any off-the-shelf AMC can still operate in any slot. Offering power and cooling at these levels is not only crucial for high-density FPGA designs today, but future-proofs for the next generation of higher power FPGAs.

COTS FPGA AMC Details   

The advent of MicroTCA.4 allows a new approach to be taken to the architecture of FPGA AMCs. The RTM allows separation of processing and I/O functionality, increasing flexibility, while the increased area and power handling on the front board allow a significant increase in the amount of FPGA logic that can be included in a product. Figure 3 outlines an example of an architecture for a high-end FPGA-based AMC card. The AMC front board focuses on maximizing the FPGA processing logic available using four of the latest Xilinx Virtex-7 FPGAs, each with dedicated DDR3 SDRAM and Flash storage. Fully meshed high-speed SERDES connections between the four FPGAs give maximum flexibility for data sharing and partition. 

Two of the FPGAs also handle external I/O: one to the AMC backplane, allowing multiple RapidIO or 10 Gbit Ethernet channels, or x8 PCI Express; and one with 8 SERDES links to the RTM. These, combined with the mesh architecture between the FPGAs, allow the system designer to implement a wide range of different data partitioning and/or data flow architectures. The main AMC front board also includes an Ethernet switch to distribute Gigabit Ethernet links to all FPGAs and to the front panel for control and maintenance purposes, as well as the  distribution of timing and synchronization from the RTM to all FPGAs.

Turning to the RTM, the example architecture uses the FPGA Mezzanine Card (FMC) standard to allow a wide range of COTS analog and digital I/O modules to be fitted. A Kintex-7 FPGA connected to each FMC site provides the high and low speed digital connections to the FMC and allows local management and control of the I/O, allowing the main FPGAs on the AMC to focus on the data processing. In addition, the RTM has a flexible PLL to manage timing and synchronization between the I/O and the AMC front board.

COTS MicroTCA.4 Platform Details

A typical MicroTCA.4 platform is 8U in height and designed for five-nines availability with redundant power supplies, fan trays and MicroTCA Carrier Hub (MCH) modules that combine the IPMI-based platform management and multiple options for fabric switching. Some platforms include an extended power option that supports up to 160W of power to each payload slot. The redundant power subsystem supports either a 100 VAC to 240 VAC or -40.5 VDC to -60 VDC input with IPMI-intelligent and hot-swappable power supplies. The cooling architecture is redundant with front-to-back push/pull IPMI-intelligent and hot-swappable fan trays. It is designed to meet NEBS and ETSI carrier-grade standards for central office deployments, as well as environments where 0° to 40°C operating temperatures are critical. Figure 4 shows an example configuration for a sensor/data acquisition and processing system.

Choosing the right platform to support an FPGA design is a critical design decision. And in today’s environment where time-to-market and development costs are a big factor, it is now more imperative than ever to consider COTS-based solutions. You may find yourself having that “Goldilocks” moment, where you find that ATCA is too large, older MicroTCA systems are too small and VPX is too expensive. The new breed of MicroTCA.4 platforms and standard AMC modules are “just right.”  

Performance Technology
Rochester, NY.
(585) 256-0200.
[www.pt.com].

CommAgility
Leichestershire, UK.
+44 (0) 1509 228866.
[www.commagility.com].