The embedded Linux community has shown considerable interest in recent months in the ARM/FPGA combo Xilinx Zynq processor, which for the first time opens up FPGA-like programmable logic functions to Linux developers. The Zynq and the similar new Altera Cyclone V SX could bring Linux into new markets in high-end industrial and military equipment, scientific research, SDR radio, and much more.
Xilinx' initial Zynq-7020 system-on-chip runs its dual Cortex-A9 cores at a modest 667MHz to 800MHz, so it may not match the latest quad-core, Cortex-A15 SoCs at multimedia. But it does have one thing the other super-SoCs don't: a powerful field programmable gate array (FPGA) capable of high-speed parallel processing. The Zynq-7020 offers 85k programmable logic cells with equivalent power to Xilinx' Artix-7. Higher-end models like the 1GHz Zynq-7100 offer up to 444k cells, much like a Kintex-7 FPGA.
The Zynq places Cortex-A9 and FPGA subsystems on a single die, connected via a high-speed AXI4 interconnect. This helps integrate processing in ways that were impossible with earlier chipsets and modules that combined ARM9 and FPGA chips. The interconnect is said to simplify the development of specialized peripherals in the FPGA fabric.
Unlike mainstream FPGAs, which require complex, time-consuming hardware description language (HDL) programming – largely beyond the control of higher-level languages and OSes -- much of the Zynq's logic is programmable by Linux via its Extensible Processing Platform architecture. Instead of depending on FPGA programmers, vendors interested in pursuing parallel processing intensive applications can tap a much larger group of embedded ARM/Linux savvy C developers, and bring products to market more quickly. With the Zynq, Xilinx has done for the FPGA what Texas Instruments accomplished with its DaVinci SoCs in making the similar, but less flexible DSP (digital signal processor) more accessible to developers.
While ARM/FPGA SoCs are luring new vendors, they are attracting customers already using FPGAs. "In most electronic systems, you will find processor-based products and FPGAs, often side-by-side," said EMEA Marketing Director Giles Peckham in an email. "Architecting designs around a single Zynq-7000 SoC enables designers to benefit from higher integration and system performance, with lower BOM costs, lower power and accelerated design productivity."
Altera Jumps in with 20nm Arria 10
The Zynq-7020 has been shipping for over a year now, and all five 28nm-fabricated models reached full production this February. A second generation of 20nm Zynq's should begin sampling this fall.
Xilinx is now beginning to face competition. Last year, FPGA rival Altera introduced its own ARM/FPGA SoC with its Altera Cyclone V SX-U672. The Cyclone V SX, which recently entered production, combines dual 800MHz Cortex-A9 cores with programmable logic equivalent to Altera’s Stratix V FPGAs. Like the Zynq, the Cyclone V SX uses an AXI interconnect to link ARM and FPGA subsystems. In May, the company began shipping its Linux-ready Cyclone V SoC Development Kit.
Last month, Altera announced a Generation 10 family of 20nm-fabricated processors, including an Arria 10 SoC due to sample in early 2014 that combines dual 1.5GHz Cortex-A9 cores with a more powerful FPGA. Other ARM/FPGA mashups include Microsemi's SmartFusion2, which can run Linux on the ARM subsystem, although on a slower 166MHz Cortex-M3 processor.
New processing frontiers for Linux
ARM/FPGA SoCs should enable further inroads by Linux into signal- and packet- processing intensive devices for machine vision, test and measurement, broadcast, military/aerospace, motor control, automotive, and scientific and medical imaging and instrumentation. Many of the early Zynq products have been software defined radio (SDR) transceivers, and higher-end models will join a new generation of ARM SoCs aimed at carrier-grade networking. In this role, ARM drives the control plane while the FPGA handles the data plane. Some server applications that demand real-time performance could also tap ARM/FPGA SoCs.
It's no wonder Denx founder Wolfgang Denk recently told Linux.com that ARM/FPGA SoC combos were one of the five hottest trends in embedded Linux.
The Zynq has a head start over Altera, and has already won numerous accolades and awards. According to the EE Times 2013 Embedded Market Study survey, when asked which microprocessors developers were planning to use, the Zynq had the largest percentage point rise, jumping from 6 percent to 13 percent.
Some other signs of the Zynq's ascent include:
- Linux CGL support -- The first ARM registration for the Linux Foundation's Carrier Grade Linux (CGL) 5.0 spec by Wind River Linux targets the Zynq. Other Linux platforms supporting the SoC include Timesys, Enea Linux, and Linaro Ubuntu Linux.
- Parallella -- Earlier this week, Adapteva began taking $99 pre-orders for its open source Parallella single board computer, which combines a Zynq running Ubuntu with Adapteva's 16-core Epiphany coprocessor. Measuring 3.4 x 2.1 inches, the Kickstarter funded Parallella is designed to build low-power, massively parallel computer clusters, such as Adapteva 42-board cluster, which runs at under 500 Watts.
- Red Pitaya -- This week, Red Pitaya launched an open source Linux measurement and control SBC on Kickstarter, and has already achieved its $50,000 goal. The $359 Red Pitaya board taps the Zync to provide a universal testing board that can be outfitted with probes and expansion modules, and accessed by web-based mobile and PC apps.
- SDR Transceivers -- Several software defined radio transceivers have tapped the Zynq. Epiq Solutions' Matchstiq Z1 handheld SDR transceiver uses iVeia's Zynq-based Atlas-I-27e computer module. A Zynq-7030 fuels the Mobilicom MCU-30 SDR radio.
- Zedboard -- In May, Avnet shipped the production version of its open-platform, Zynq-7020-based Zedboard SBC. The $395 ZedBoard is offered with a Linux reference system and a ZedBoard.org community site, and provides expansion connectors that expose I/O from the ARM and FPGA subsystems.
ARM/FPGA combos like the Zynq are not ideal for everyone. They're more expensive and harder to master than most mainstream ARM SoCs, and many projects still require some HDL programming. Yet, this new wave of processors has taken a huge leap in bringing Linux developers closer to the arcane world of FPGAs.