JAM: A to Z – Overview of Gavin Wood’s Keynote at Sub0

Discover JAM: Gavin Wood's innovative blockchain concept enhancing efficiency and scalability, potentially succeeding Polkadot's relay chain.
jam a to z

In a recent keynote at Sub0, Gavin Wood provided an extensive overview of JAM, a cutting-edge project under development at Parity Technologies. Designed as a potential successor to the Polkadot relay chain, JAM introduces several innovative concepts poised to reshape blockchain technology. Here’s an in-depth look at the key points from Wood’s presentation.

What is JAM?

JAM, short for Join Accumulate Machine, is a novel blockchain concept designed to improve and extend the capabilities of Polkadot. The acronym JAM originates from its computational model: Collect, Refine, Join, Accumulate.

Key Objectives:

  • Simplification and Optimization: JAM aims to provide a more streamlined and efficient approach to blockchain technology, reducing the complexity and improving the performance of current systems. This is achieved by focusing on essential functionalities and eliminating redundant processes, thus making the system more robust and easier to maintain.
  • Generalization and Abstraction: By lowering the level of opinionation, JAM offers a more generalized platform that can handle a wider range of applications. This means that the blockchain can support diverse use cases without being tied to a specific protocol or framework, enhancing its versatility and adaptability.

Core Components of JAM

JAM is a Domain-Specific Chain

JAM is not a general-purpose chain. Instead, it focuses on specific tasks, much like a smart contract chain but with unique differences and enhancements. This specialization allows JAM to optimize for particular types of computations and operations, making it more efficient for those use cases.

JAM Work Packages and Refinement

  • Work Items and Packages: JAM handles inputs through work items, which are processed in work packages. These packages can contain multiple work items, each representing a distinct unit of work that needs to be processed.
  • Refinement and Accumulation: The refinement process transforms work items into work results, which are then accumulated into the shared state. This two-stage process ensures that each work item is processed accurately and efficiently before being integrated into the global state.

JAM State and Services

Services Model: JAM introduces a service-oriented architecture, where each service encapsulates code, balance, and state. This model allows permissionless creation of new services, similar to smart contracts. Services can be created and managed independently, providing a modular approach to building blockchain applications.

  • Permissionless Creation: Anyone can create a new service without needing special permissions, promoting decentralization and innovation.
  • Service Lifecycle: Services in JAM have a lifecycle that includes creation, execution, and eventual termination or upgrade, providing a structured way to manage applications on the blockchain.

JAM Technical Innovations

PVM (Parachain Virtual Machine)

  • Risk-V Based:The PVM is based on the RISC-V instruction set, offering simplicity and security. RISC-V is a highly flexible and open standard, which makes it ideal for blockchain applications that require customization and scalability.
  • Metering and Continuations: The PVM supports secure metering and continuations, facilitating more efficient and scalable computations.

Consensus Algorithm

  • SAFFRON-Based: JAM uses the SAFFRON consensus algorithm, a simplified and optimized version of SASAFRAS, ensuring efficient and secure block production.

Advantages of JAM

Reduced Opinionation

JAM reduces the inherent opinionation found in Polkadot, making it more adaptable to various use cases without compromising security. This generalization allows developers to implement a wider range of applications and use cases on the future JAM chain.

Permissionless and Scalable

The permissionless nature of JAM allows for the easy creation and integration of new services, promoting innovation and scalability. This model ensures that developers can experiment and deploy new ideas without being restricted by existing governance structures.

Agile Core Time and Substrate Integration

  • Agile Core Time: JAM maintains the concept of agile core time, enhancing its flexibility and usability. Agile core time allows for dynamic allocation of computational resources, ensuring that high-priority tasks are handled efficiently.
  • Substrate Tooling: Integration with Substrate ensures that existing tools and ecosystems can easily adapt to JAM’s architecture. This compatibility means that developers familiar with Substrate can quickly transition to developing on JAM, leveraging existing knowledge and tools.

JAM Deployment and Future Steps

Testing and Implementation

  • Jam Toaster: A comprehensive test rig named Jam Toaster will be used for full-scale trials and monitoring. This test environment will simulate a full-scale JAM network, providing valuable insights into its performance and identifying any potential issues before deployment.
  • JAM Roadmap (timeline): The proposed timeline for JAM includes several stages: proposal drafting, initial implementations, RFC discussions, and final deployment, expected to span from 8 to 20 months. Each stage involves careful planning and execution to ensure that JAM meets its design goals and integrates smoothly with existing systems.


JAM represents a significant leap forward in blockchain technology, promising to enhance efficiency, scalability, and flexibility. With its innovative design and integration capabilities, JAM is poised to become a crucial component of the blockchain ecosystem, potentially succeeding the current Polkadot relay chain.

For developers and blockchain enthusiasts, JAM offers a new frontier of possibilities, making it an exciting development to watch in the coming months.

Bangkok event
All the content of Polkadot Sub0 2024
Videos, summaries,
related resources...
Table of Contents

Follow us on X to discover our latest content.

Related Content
Polkadot Sub0 2024 Featured Content