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(Image courtesy of Gareth Halfacree, Creative Commons).

A Patient Disciple, SiFive Starts Selling RISC-V Cores

Jack Kang, the company's vice president of product and business development, told Electronic Design that customers had been asking for commercial licenses to its RISC-V cores.

Last year, SiFive went fishing for engineers to test out chips based on the RISC-V instruction set, releasing an embedded core called Rocket that anyone could download and modify. But now the company, whose founders invented RISC-V, is using richer bait for more ambitious customers.

Last week, SiFive started selling two cores under the brand Coreplex for applications like wearables and servers. The company aims to make it easy for engineers trained on Intel or ARM instruction sets to take RISC-V for a spin. But it is working against the fact that few engineers appear to be turned off by the licensing fees or inflexibility of rival technology.

Licensing the cores takes little more than signing an online contract and making a one-time payment, which will cost less than a million dollars. It is also making the register transfer level – more commonly known as the RTL – available immediately, so that chip designers can simulate particular designs.

The announcement is a mile marker for the year-old business. SiFive is trying to stamp a claim on the RISC-V architecture, which provides starting instructions for creating a chip and which promises to reduce the millions of dollars and years of development required to make chips for markets like the Internet of Things.

SiFive is using the new instruction set to design chips ahead of time, filling in the blanks with its own custom technology or working with customers on unique designs. Its business model is similar to how Red Hat Software started selling its expertise with the free Linux operating system.

“Since the company was founded, we have actually had lots of requests from customers,” said Jack Kang, SiFive’s vice president of product and business development, in an interview last week. “They said, it’s nice to have open-source cores, but we want a commercial license that a company is behind and is well-supported.”

The Coreplex intellectual property includes two designs. The E31 core is a 32-bit processor that can replace the ARM Cortex M3 inside sensors and wearables, while the E51 core is a 64-bit embedded processor designed to serve as a controller in large chips or SoCs.

SiFive is trying to make it as easy as possible for engineers to experiment with its chips, since its biggest hurdle is building a community of RISC-V developers. It is not charging royalty fees, meaning that it gets nothing more than the one-time payment of $275,000 for the E31 and $595,000 for the E51.

Its sales strategy aims to eliminates many of the usual snags for licensing cores: engineers will not have to contact a salesperson or sign a non-disclosure agreement to view datasheets and specifications. If companies want to purchase the cores, they only have to sign a seven-page contract. There is no need for negotiation.

“In royalty-based models, companies have to know exactly what you are making and how many there will be,” Kang said. “But you can buy enterprise software online directly without talking to anyone. So we asked: why not bring that to hardware?”

RISC-V lets companies modify the basic instructions inside their chips, using a modular design that allows engineers to add custom extensions. That contrasts with Intel and ARM, both of which tightly control their instruction sets. Using RISC-V, companies control more of the chip's design, cutting down on money and time required for customization.

That has clearly intrigued companies looking into custom chips, especially ones trying to squeeze performance out of data centers. The RISC-V Foundation, which maintains the instruction set, includes members like Google, Microsoft, and Oracle, as well as IBM. Their engineers are frequent attendees at RISC-V meetings.

But the instruction set has also won over large semiconductor companies. After evaluating ARM, MIPS, and other embedded architectures, Nvidia started using RISC-V in the controllers for its graphics chips. Microsemi, one of SiFive's first customers, is already using Coreplex technology in its Igloo and other FPGA chips. 

Investors are also betting on open hardware. SiFive, whose founders – Krste Asanovic, Yunsup Lee and Andrew Waterman – are also active with the RISC-V specification, announced Monday that it had raised $8.5 million from Spark Capital and other investors. The start-up previously raised $5 million in its first funding round.

The start-up also said Monday that it had sold over a thousand of its Freedom development boards, which it released in November through a crowd-funding campaign. Its customers can tinker with the register transfer level inside the chips, offering customization that SiFive handles itself in the Coreplex designs.

The company doesn't view Coreplex as a repudiation of its open-source roots, though. “It’s still the early days for RISC-V, so lots of companies initially decided to try it without actually understanding what ‘free and open’ means," said Kang. "The biggest surprise is that it isn’t exactly what they were initially looking for.”

“But I think the sign of momentum is that companies say that they want more from us," said Kang. "We’ve really been surprised by how quickly RISC-V has grown.”

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