JAM Chain TOKEN2049

Polkadot JAM Chain

Join-Accumulate Machine

Polkadot’s JAM Chain is a revolutionary, scalable, and transactionless blockchain enhancing roll-ups and smart contract functionalities. +info on the Polkadot Wiki.

Exploring Polkadot's JAM Chain: A Comprehensive Overview

Polkadot, a prominent blockchain platform known for its scalable and interoperable network, is poised to introduce a groundbreaking project known as JAM Chain. JAM, an acronym for Join-Accumulate Machine, represents a visionary shift aimed at enhancing the Polkadot ecosystem. The concept of JAM originates from CoreJAM, a model conceptualized by Gavin Wood, emphasizing the processes of Collect, Refine, Join, and Accumulate. However, within the JAM Chain, only the Join and Accumulate functions are executed on-chain, while Collect and Refine occur off-chain.

The Shift to a Unified Upgrade

Unlike the conventional iterative upgrade approach, JAM will be deployed as a comprehensive, singular upgrade. This method offers several advantages:

  1. Controlled Post-Upgrade Actions: A unified upgrade allows for precise control over post-upgrade actions, which is challenging with an iterative approach.
  2. Reduced Minor Upgrades: It mitigates the constant stream of minor upgrades and breaking changes, providing a more stable environment.
  3. Minimized Impact: While this shift entails a significant breaking change, efforts will be made to manage its impact effectively, consolidating multiple smaller changes into a single transition.

A Rollup Chain for Domain-Specific Solutions

JAM will function as a domain-specific chain, primarily focusing on roll-ups. Polkadot has already established itself as a highly domain-specific roll-up chain over the past five years. JAM aims to generalize this approach, making it less opinionated and more versatile. The JAM chain accepts outputs of roll-ups, integrating them into a shared state, similar to the Polkadot Relay Chain. Its primary function is to ensure that the output accurately reflects the input after undergoing the intended transformation.

JAM Smart Contract Similarities and Service Entry Points

JAM shares several similarities with a smart contract chain:

  1. Permissionless Code Execution: Code execution on JAM is permissionless, occurring directly on the chain.
  2. State Encapsulation: The state of JAM is organized into distinct encapsulations called services, which include code, balance, and state components.
  3. Service Creation: Creating a new service on JAM is permissionless, akin to deploying a smart contract, and does not require governance approval.


polkadot jam

JAM services have three entry points:

  1. Refine: Handles stateless computation, defining transformations for roll-ups.
  2. Accumulate: Integrates the output of Refine into the overall state of the service.
  3. OnTransfer: Manages information from other services.

Work packages serve as inputs to services, containing work items associated with specific services. The JAM security apparatus involves a two-stage process where Refine accepts work items and produces work results, which are then processed by Accumulate.

Transactionless Operations and Extrinsic Information

JAM distinguishes itself by operating transactionlessly. Instead, it handles extrinsic information in five formats: Guarantees, Assurances, Judgments, Preimages, and Tickets. These elements form part of JAM’s security framework, ensuring validators attest to the accuracy of work results.

JAM Chain Technical Architecture: Refine, Accumulate, and OnTransfer Functions

The Refine function processes up to 15 MB of data within each time slot, yielding a maximum of 90 kB of data. This stage is crucial for data compaction due to the distributed nature of the availability system. Refine can execute for up to 6 seconds of Polkadot Virtual Machine (PVM) gas.

The Accumulate function integrates the output from Refine into the chain state. It is stateful, allowing access to the JAM chain’s state and enabling various functionalities such as creating new services and transferring funds.

The OnTransfer function facilitates asynchronous communication between services, enabling state modifications and interactions.

JAM Chain Generalization and Enhancements

JAM represents a significant reduction in opinionation compared to Polkadot, offering higher abstraction and generalization. It operates in a permissionless manner, allowing users to upload and execute code, host data, and manage state. JAM also supports features like preimage lookup and managing key-value pairs.

Polkadot Virtual Machine (PVM) and SAFROLE Algorithm

The PVM design is based on the RISC-V ISA, known for its simplicity and versatility. This architecture ensures high execution speeds and efficient metering. SAFROLE, a block production algorithm, simplifies the process by excluding unnecessary components, maximizing potential future use cases.

JAM Chain Networking and Pipelining for Efficiency

JAM utilizes the QUIC protocol for networking, facilitating direct connections between validators and avoiding gossip protocols. Pipelining in JAM enhances block processing efficiency by adopting a different approach to state roots, allowing more time for computation.

Architectural Distinctions: JAM vs. Relay Chain

JAM introduces fixed parameters for optimizations, unlike the highly upgradable relay chain. This approach reduces complexity and enhances optimization possibilities. JAM retains flexibility through its service model, managing coretime sales, staking, and governance at the application level.

JAM Toaster: Comprehensive Testing Platform

To meet its objectives, JAM introduces the JAM toaster, a test platform designed for large-scale trials and performance assessments. This platform enables in-depth research at the scale of the entire JAM network, providing valuable insights for developers.

JAM Chain Compatibility and Future Enhancements

JAM maintains compatibility with existing Polkadot parachains while introducing significant enhancements. It supports benchmarking, Cross-Chain Message Passing (XCMP), and introduces the concept of accords for secure interactions between parachains.


Polkadot’s JAM Chain represents a transformative step in blockchain technology, offering a flexible and efficient framework for managing data and computations. By integrating roll-up functionality, smart contract similarities, and advanced networking protocols, JAM aims to revolutionize the Polkadot ecosystem, providing a scalable and robust platform for future developments.

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