Arm, Under Pressure From Free and Open Source Silicon, Launches Custom Instructions Offering

Cambridge-based low-power computing giant Arm, facing increasing pressure from the free and open source silicon (FOSSi) movement in general and the RISC-V instruction set architecture in particular, has announced that it is to allow customers to specify custom instructions to be added to its Armv8-M architecture for the first time.

Arm's processor intellectual property is undeniably popular. Born from British microcomputing pioneer Acorn Computers, and originally an acronym for Acorn RISC Machines, Arm's chips are found in almost every phone and tablet in the world plus innumerable embedded devices and popular development boards.

The company's approach, however, is a somewhat prescriptive one: Even its biggest customers are licensed the proprietary core IP under restrictive terms, under pricing that leaves all but the largest forced to buy off-the-shelf chips at one remove. This contrasts markedly with the growing free and open source silicon movement, in which the core instruction set architecture and many implementations are made available under permissive licences - requiring no up-front fees, no ongoing royalties, and offering the ability for users to alter the implementation as they see fit.

Facing an increasing number of its customers dabbling in FOSSi, and in particular the popular RISC-V ISA, Arm has responded with the Custom Instructions offering — enabling customers licensing Arm IP for use in system-on-chip designs to add their own instructions to the ISA for the first time.

"A world of a trillion secure intelligent devices will be built on a diversity of complex use cases requiring increased synergy between hardware and software design," says Dipti Vachani, senior vice president and general manager for Arm's automotive and IoT lines of business, of the move. "We have engineered Arm Custom Instructions to fuel closer hardware and software co-design efforts toward achieving application-specific acceleration while unlocking greater device differentiation."

The Arm Custom Instructions program will launch in the first half of 2020, offering licensees the ability to extend the core Armv8-M architecture with their own instructions at no added cost. Initially, the program will be available exclusively on the Arm Cortex-M33 core; Arm has yet to confirm plans to extend it to other IP.

"Arm’s new Custom Instructions capabilities allow silicon suppliers like NXP to offer their customers a new degree of application-specific instruction optimisations to improve performance, power dissipation and static code size for new and emerging embedded applications," claims NXP Semiconductors general manager for microcontrollers Geoff Lees in support of the move. "Additionally, all these improvements are enabled within the extensive Cortex-M ecosystem, so customers’ existing software investments are maximized."

Developer information for the Arm Custom Instructions program can be found on the Arm website now.