An instruction set architecture (ISA) is crucial to the development of processors and their software ecosystems. In the last half century, the majority of ISAs have been owned by single companies, whether product companies for their own chips/systems or processor IP companies who licensed their processors to chip developers. Does ISA ownership matter? Let’s consider three proprietary ISAs and their history.
Firstly, the Alpha ISA was developed by Digital Equipment Corporation (DEC) for its workstations and servers and was released in 1992. In the mid-1990s, this was considered a worthy competitor to SPARC and MIPS RISC architectures. However, the ownership of the ISA transferred to Compaq when DEC was acquired in 1998. Compaq in turn sold the rights to the Alpha ISA to Intel in 2001, and in the same year Compaq was acquired by Hewlett Packard. The last Alpha-based products were released in 2004, meaning that the ISA was effectively dead because of a series of acquisitions.
MIPS Technologies was spun out of Silicon Graphics as an independent IP company in 1998. For some years it enjoyed some success, particularly at the higher end of the processor IP market, and was only the second architecture to have Android ported in 2009. However, with a declining share price, MIPS sold 498 patents to AST and agreed to an acquisition by Imagination Technology in 2013. After Canyon Bridge acquired Imagination, MIPS was spun-out again ending up, after a series of transactions, as part of Wave Computing. As an artificial intelligence silicon provider, Wave is a potential competitor to some MIPS licensees.
Wave tried to encourage the adoption of the MIPS ISA in competition to RISC-V through their MIPS Open Initiative in late 2018. However, the licensing terms contained some onerous conditions relating to patents. In late 2019, Wave suddenly shut down the program, giving zero notice. The important lesson is that even if an ISA is open, its future is not secure if it is commercially owned. Seven years of ownership change have seen MIPS’ market share spiral downwards.
The third example is Arm, the biggest processor IP company of them all. Arm has long been seen as not only a big, successful IP company, but one offering “Swiss neutrality” in the semiconductor industry. Arm was quite distinct from both semiconductor companies and EDA companies. As such, it enjoyed a position of trust from its licensees as it did not have a conflict of interest. With its acquisition by SoftBank in 2016, Arm lost control over its destiny, even though SoftBank was not competing with its licensees. With the planned acquisition of Arm by NVIDIA, announced in September 2020, Arm will lose its neutrality completely. As a semiconductor company, there is a conflict of interest between Arm’s owners and its licensees, meaning it can no longer be trusted in the same way.
As can be seen from the ‘Tale of three ISAs’, the ownership of an ISA matters a lot, regardless of whether the ISA is commercially licensed or open. Acquisitions can lead to the disappearance of an ISA through merging of product lines or through making licensing difficult. Another motive for taking over a company can even be to kill off a competing product line, which in the case of an ISA could catastrophically impact licensees.
ISA ownership is one of the key issues that the developers of RISC-V have thought about. By transferring the ownership of the ISA to RISC-V International, the original developers of the ISA have assured its longevity. Longevity is assured both by the independent ownership of the ISA and the fact that licensees have a choice of IP vendors supporting the same open standard. Thirdly, once ratified, the ISA is frozen assuring software developers that their code will be able run on suitable cores indefinitely.