XISA is the instruction set architecture for Xsight X-Series Ethernet switches — the interface you program the silicon through. It covers the programmable parser and the match-action processor, including instruction formats, encodings, semantics, and the register model. The full XISA specification document is available under the Mozilla Public License version 2, with no NDA or purchase required.
Switch silicon has traditionally been a black box. You get an SDK, a set of APIs, and a support contract, and the behavior of the chip underneath is a matter of trust. Publishing the instruction set changes that arrangement: the interface your engineers write against becomes a public document rather than a private contract. This page sets out what we opened, why, and what it enables.
We published the full instruction set in March 2025. Not a summary or an API reference, but the same document our own engineers work from, covering both the parser and the match-action processor.
The reason was practical. A customer needed a P4 compiler for X-Switch to move from another vendor's silicon. We could have built that compiler ourselves and kept the instruction set closed. Instead, we opened it.
That decision reflects a broader view of where the switching market went wrong. Consolidation and vertical integration in this market have worked against the disaggregated networking that drove cloud computing at hyperscale. As our CTO, Gal Malach, put it when we announced the initiative:
“Opening the Switch ISA unlocks the inherent flexibility of the X-Series, enabling customers to tackle everything from traditional applications to the most complex use cases with ease.”
Gal Malach
CTO and Co-Founder, Xsight Labs
The practical logic is straightforward. If the instruction set is public, anyone can build tooling for it without our involvement or permission — compilers, debuggers, analyzers, and more. A closed ISA means every piece of tooling has to come from us, on our schedule, and according to our priorities. That creates a bottleneck for customers and, frankly, for us.
All three from the 25 March 2025 announcement.
“We at Oxide believe in programmable networking silicon but have been frustrated by vendors' insistence on keeping their instruction set architectures secret.”
Bryan Cantrill
Co-Founder and CTO, Oxide Computer Company
“By open-sourcing its ISA, Xsight Labs is empowering developers and the broader industry to push the boundaries of networking innovation, enabling the development of a P4 compiler.”
Andy Fingerhut
Chair, P4 Consortium Technical Steering Team
“Opening up switch architectures mirrors the profound shift Linux brought to CPU networking and will drive significant advancements.”
Alan Weckel
Founder and Technology Analyst, 650 Group
“Open” is widely used, and often loosely defined, in networking. So it is worth being precise about what we mean by it, and what we don't.
It does not mean the silicon is open source. The chip is our design and our intellectual property; what is open is the interface you program it through.
It does not mean you have a second source. Xsight is currently the only company implementing XISA. An open specification is independently implementable in principle, but nobody else ships it today. Anyone who tells you an open ISA eliminates supplier dependency is overstating what it does.
These are the three main ways that open ISA can benefit your operations, listed in the order most teams encounter them. Explore each one in depth across this hub.
When the data path is programmable and the instruction set is published, adding support for a new protocol becomes an engineering task rather than a procurement decision. That is the difference between a capital problem and a scheduling one.
UEC, new congestion algorithms, RDMA, and QUIC each arrive expecting silicon that did not exist when the budget was set. On fixed-function silicon, you wait for the next generation, deploy the function somewhere more expensive, or bring a refresh forward. On a programmable data path with a documented instruction set, you write the change, test it, and deploy it to hardware already in the rack. Our tutorial on adding counter tables shows exactly this: new measurement capability added to a program already in production, without touching the parser at all.
→ Read the full argument: Future-proofing without a refresh, deploying new protocols without buying new silicon.
Every switch vendor now claims programmability, and almost none mean the same thing. A published instruction set lets you check the claim directly: read what the parser can traverse, what the match-action processor can hold, which operations are accelerated, and what each costs in instructions.
The distinction matters because the differences are rarely visible in a datasheet. Whether a table can be read more than once per packet, whether adding logic forces recirculation, or whether a new header format requires a feature request: these determine what you can actually build, and they are answerable from the specification rather than from a conversation with a salesperson.
→ Use the evaluation checklist: Ten criteria for assessing switch programmability, with the questions to ask any vendor, and the XISA glossary for the terminology.
Data-path code written against a proprietary SDK targets an interface that exists in exactly one company. Code written against a published specification targets a document you can read, keep, and reason about, regardless of whether you remain our customer.
This is the part teams underestimate, because the code looks like theirs either way. The test is not whether you wrote it; it is whether that investment is portable. On a mature deployment the accumulated engineering investment routinely exceeds the cost of the hardware it runs on, and unlike the hardware, it appears on no asset register.
→ Assess your own exposure: Avoiding vendor lock-in when switching silicon, covering the three dependencies that drive exit cost and the criteria you can apply to any supplier, including us.
Five worked programs that build on each other, from a five-instruction cross-connect to in-network computation. Each one is a complete, annotated XISA program.
Analyst perspective from Wheeler's Network, commissioned by Xsight, plus the specification itself.
Speak with our solutions team to explore your infrastructure requirements and discover how open silicon could work for your environment.