Innovation often emerges from recognizing connections between seemingly disparate fields. This is precisely the story behind Clash, a groundbreaking compiler that revolutionized how engineers could approach hardware design. The journey of the creators of the Clash compiler began in the corridors of academia, where theoretical computer science met practical hardware engineering
The Creators of the Clash Compiler: A Story of Academic Innovation
The Spark of Inspiration
The story begins with Jan Kuper, an academic who found himself transitioning from the theoretical informatics department to computer architecture. Kuper needed to align his courses with his new department’s focus, while still sharing his knowledge of the theory behind how computers work. This led him to collaborate with colleagues on a course about designing computer architectures.
While teaching this class, Kuper had a moment of insight that would change the trajectory of hardware design tools. He noticed striking similarities between certain aspects of functional programming (which he had been teaching) and the process of designing computer architectures. This observation prompted him to modify his course, introducing a novel approach: using a functional programming language for computer structure design.
From Concept to Compiler
The step from teaching to creating a functional tool for chip designers came in 2009. Kuper was already using the functional programming language Haskell to design computer structures in his courses, but there was a significant limitation—he couldn’t implement these designs on an FPGA (Field Programmable Gate Array) because FPGA software only accepted established languages like VHDL and Verilog.
This is where, later co-founder of QBayLogic, Christiaan Baaij enters the picture as one of the key creators of the Clash compiler. Baaij, along with fellow student Matthijs Kooijman, approached Professor Gerard Smit seeking a graduation assignment. Around the same time, they connected with Jan Kuper, who expressed his desire for a compiler that could translate his Haskell code into VHDL, allowing his designs to be implemented on actual FPGAs.
An Unusual Collaboration
In what Christiaan describes as “an exceptional situation,” the university allowed two students to work together on a single graduation project—something typically not permitted. Baaij and Kooijman divided the tasks sufficiently to convince the examination committee that each student would complete substantial individual work.
Beginning in January 2009, the two students embarked on building the first version of the Clash compiler. Working under an ambitious timeline, they completed the initial version just in time to present it at the Haskell Symposium in September 2009. This early version successfully demonstrated the translation of functional Haskell code into standard VHDL for FPGA designs.
The formal report describing their work came later. A testament to the priority they placed on functional completion over documentation, driven by the conference deadline.
From Academic Project to Open Source Innovation
After graduating, Christiaan continued developing Clash during his PhD research, further refining and expanding its capabilities. From the beginning, the creators ensured that Clash remained open source, even as the intellectual property considerations changed when Baaij became a university employee. The creators of the Clash compiler were committed not just to making the source code available but to fostering an active community around the tool. They encouraged users to report bugs, contribute improvements, and participate in the ongoing development of the platform.
They maintained this commitment to open source, even as they transitioned from academia to industry. The intellectual foundations laid during those university days continued to guide the development of Clash, ensuring it remained accessible to users worldwide.
QBayLogic: Sustaining the Vision
In 2016, Jan and Christiaan founded QBayLogic, to “keep Clash alive” and to apply it in industrial settings. Recognizing that some improvements needed for industrial applications were difficult to justify in an academic research context, this move allowed the creators of the Clash compiler to focus on practical enhancements.
These included better integration with existing languages like VHDL and Verilog, making it easier to incorporate components already written in these languages into Clash projects. This pragmatic approach has helped bridge the gap between innovative design methodologies and established industry practices.
What Makes Clash Unique
What distinguishes Clash from other hardware description languages is its approach to circuit design. While other modern languages, such as Chisel or Amaranth, might provide a “recipe” for a robot or factory to build a circuit, Clash allows engineers to describe the circuit directly as a normal Haskell program.
This direct translation approach is particularly valuable during the creative process of circuit design. As Christiaan explains, when facing a problem with millions of possible solutions, the human brain needs to quickly eliminate vast swathes of possibilities. Clash’s approach, treating hardware design more like standard programming, facilitates this creative engineering process.
Legacy and Impact
Today, Clash is used worldwide by hardware designers who appreciate its unique approach to digital circuit design. The vision of its creators—to bring the power of functional programming to hardware design—has materialized into a tool that bridges theoretical computer science and practical engineering.
The story of the creators of the Clash compiler is one of academic innovation meeting practical application and as such illustrates what QBayLogic stands for. Having made the journey from a university classroom observation to an industry-standard tool, Clash represents how innovative thinking, combined with technical expertise and collaborative effort, can create solutions that transform an entire field of engineering.
