M OST MICROPROCESSORS —the chips that do the grunt work in computers—are built around designs, known as instruction-set architectures ( ISA s), which are owned either by Intel, an American giant, or by Arm, a Japanese one. Intel’s ISA s power desktop computers, servers and laptops. Arm’s power phones, watches and other mobile devices. Together, these two firms dominate the market. Almost every one of the 5.1bn mobile phones on the planet, for example, relies on an Arm-designed ISA . The past year, however, has seen a boomlet in chips made using an ISA called RISC-V . If boomlet becomes boom, it may change the chip industry dramatically, to the detriment of Arm and Intel, because unlike the ISA s from those two firms, which are proprietary, RISC-V is available to anyone, anywhere, and is free.

An ISA is a standardised description of how a chip works at the most basic level, and instructions for writing software to run on it. To draw an analogy, a house might have two floors or three, five bedrooms or six, one bathroom or two. That is up to the architect. An ISA , however, is the equivalent of insisting that the same sorts of electrical sockets and water inlets and outlets be put in the same places in every appropriate room, so that an electrician or a plumber can find them instantly and carry the correct kit to connect to them.

RISC-V offers computer architects a way to standardise their sockets and plumbing without having to gain permission from (and pay royalties to) either of the monopolists—for any company or individual may download it from the internet. It was originally written by computer scientists at the University of California, Berkeley, who wanted an instruction set that they could use for publishable research. Commercial producers of ISA s were reluctant to make theirs available, so the academics decided to buckle down and write their own.

The result, RISC-V , made its debut in 2014, at the Hot Chips microprocessor conference in California. It is now governed by a non-profit foundation. Though there are no formal royalties, the foundation does solicit donations as pro bono publico gestures from firms that employ RISC-V architecture—for what was once a tool for academics is now proliferating commercially.

There are three reasons for this proliferation. The most obvious is that the lack of royalties means using RISC-V is less costly than employing a commercial ISA . If the final product is a high-price object like a smartphone, that may not be a huge consideration. But for cheaper devices it is. Moreover, as chips are built into a growing range of products, such as home appliances, city infrastructure and factory equipment, it makes business sense to keep them as cheap as possible.

A second, more subtle advantage is that, unlike chips based on proprietary designs, those involving RISC-V can be used without lengthy and expensive contractual negotiations. It can take between six months and two years to negotiate a licence to use a chip design involving a commercial ISA . In the world of computing, especially for a cash-strapped startup, that is an eternity.

The third reason people are shifting to RISC-V is the nature of open source itself. Since the instruction set is already published online, American export controls do not apply to it. This has made it particularly popular with Chinese information-technology firms. Alibaba, an e-commerce giant based in Hangzhou, announced its first RISC-V chip in July. Shanghai’s municipal government has a programme which supports startups using RISC-V in their designs. Huami, a big wearable-device firm in Hefei, is mass producing smart watches containing processors based on RISC-V . And in Shenzen, Huawei, one of the world’s largest electronics companies, has a team of developers working on RISC-V . In an interview in September Wang Chenglu, the boss of Huawei’s consumer-electronics business, pointed to the RISC-V foundation’s recent move to Switzerland, out of America’s jurisdiction, as something that will encourage Huawei’s use of the ISA .

RISC-V does have weaknesses. Arm has spent decades building software tools to work with its designs, and spends a lot of its time helping customers implement these on their chips. The tools that exist for RISC-V designs are not yet that sophisticated. Intel makes things simpler still. It carries out all of the development, testing and fabrication itself, delivering only finished chips to customers. This reliability will certainly keep these firms’ products competitive for a while.