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Monday, July 11, 2016

Reinventing MIPS as an open source chip venture

By Nick Flaherty

I've championed open source hardware over the years (which tells you it has been tried quite a few times before) but the latest family of system-on-chip designs from SiFive looks somewhat like the re-birth of MIPS as an open source play.

The Freedom family of SoC platforms launched by SiFive uses the free and open RISC-V architecture and ecosystem that its founders also developed at the University of California (sound familiar at all?). This, they say, will democratise access to custom, state-of-the-art semiconductors. The devices are being built on 28nm for a 64bit multicore Linix implementation, so not that state-of-the-art, or 180nm for the 32bit low cost IoT market with various peripherals. Hmmmm.
The U500 64bit multicore open source processor from SiFive 
You might also like: Microchip adds independent peripherals to PIC32

The Freedom platforms (which unfortunately is reminiscent of Freedom Fries) comprise a complete software specification, board OS support packages (BSPs) which is good, development boards and base silicon. The platforms provide customers the ability to create their own silicon enhancements and customisations, which SiFive then quickly incorporates and delivers to the customer at a much lower cost and faster time-to-market than traditional custom silicon designs. They say this also provides significant performance and power advantages over existing microcontrollers and FPGAs, which is true but also a benefit delivered by many other custom and semi-custom design houses.

"The semiconductor industry is at an important crossroads. Moore's Law has ended, and the traditional economic model of chip building no longer works," said Yunsup Lee, co-founder of SiFive and one of the original creators of RISC-V. "Unless you have tens — if not hundreds — of millions of dollars, it is simply impossible for smaller system designers to get a modern, high-performance chip, much less one customized to their unique requirements."

There's quite a lot of design houses that would contradict this - I write about many of them here (!) -  but it gets the message out there. But what it does do it fragment the MIPS market even further than it is already.

The founders say RISC-V was born from the dire need to address the skyrocketing cost of designing and manufacturing increasingly complex new chip architectures. SiFive's hardware designs make use of software and tools available from the open-source community under the guidance of the RISC-V Foundation, which reduces the cost of developing custom silicon. System designers can use the SiFive Freedom platforms to focus on their own differentiated processor without having the overhead of developing a modern SoC, fabric or software infrastructure.

"RISC-V represents a bold new path for system designers in embedded and industrial markets," said Ted Speers, head of product architecture and planning for Microsemi Corporation's SoC business unit, which has produced some development boards for SiFive. "We went to SiFive not only because its co-founders created RISC-V, but also due to its team's agile methodology, which enabled the company to deliver a complete RISC-V sub-system and tool-chain targeting our secure, low power SmartFusion2 SoC FPGA platform on a very aggressive schedule."

The two platforms are: 

Freedom U500 Series with a fully Linux-capable embedded application processor with multicore RISC-V CPUs, running at a speed of 1.6 GHz or higher with support for accelerators and cache coherency. Designed in TSMC 28nm, the Freedom U500 platform targets initial customers in diverse markets such as machine learning, storage and networking. The Freedom U500 platform also supports standard high-speed peripherals including PCIe 3.0, USB 3.0, Gigabit Ethernet, and DDR3/DDR4.

The E300 series of open source 32bit microcontroller
 using the RISC-V instruction set architecture 
 The Freedom E300 Series (above) is designed for embedded microcontroller, IoT and wearables markets. Designed in TSMC 180nm and architected to have minimal area and power, the Freedom E300 platform features the world's most efficient RISC-V cores with support for RISC-V compressed instructions, which have been shown to reduce code size by up to 30 percent.

All this is very reminiscent of the MIPS roadmap, and under Imagination Technologies the architecture was available as open source.

To give developers a head start on software development, full FPGA models of each SoC are available through SiFive so they can prototype their customisations in the form of custom RISC-V instructions, accelerators and co-processors. For more information, including how to purchase development boards with the Microsemi SmartFusion2 SoC FPGA, please visit

SiFive will showcase the Freedom family of SoC platforms during the RISC-V 4th Workshop in Boston on Tuesday, July 12.

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