JAM still needs quite a bit of time, and currently, the first RISC-V VM that is close to being put into production is PolkaVM (another one is the @boundless_xyz zkvm, which is already on the mainnet beta version and also based on RISC-V VM, but it is a more zk version of the VM). It has already gone live on KSM (the early platform of @polkadot). It went live around June and is now relatively fully compatible with Solidity smart contract development. The demo program has implemented the complete operation of the Uniswap V2 version and is compatible with the Ethereum toolchain (Remix, Hardhat), and can integrate with popular libraries.
On this basis, a recent important update is XCM-Precompile (XCM's precompiled version, where XCM stands for cross-chain transfer protocol), which supports cross-contract calls at the language level. By inheriting or importing the IXcm interface, XCM functionality can be directly integrated into existing smart contracts. This method allows you to seamlessly embed cross-chain functionality into application logic. Whether building DeFi protocols, governance systems, or any applications that require cross-chain coordination, XCM calls can be directly incorporated into the contract's functionality. The Polkadot version of the RISC-V VM - PolkaVM should go live alongside the Polkadot Hub.
Polkadot ecosystem developer @alice_und_bob has predicted the roadmap and timelines for the second half of the year (which may not be absolutely precise):
- Polkadot 2.0 - Elastic Scaling (August?)
- Polkadot Hub - developer and user onboarding platform (October?)
- Polkadot Pay - mobile app (August?)
- DOT ETFs (whether it goes through will ultimately be in November)
- DOT Tokenomics 2.0 (still under discussion)
His roadmap is quite good:
XCM-Precompile:
PolkaVM live on Kusama:
JAM是2.0之后，就是正在加速研发的，超过30多个团队，不同编程语言，不同开发团队来实现分散的JAM客户端（基于JAM灰皮书协议来实现的）。
最早的ETH，是所有交易，要所有验证人一起验证一遍（这一部分其实可以看看以太坊黄皮书，还有一个更好的解读版本
L2是让链下一个更小的子集进行计算，通过两种方式，一种L2是欺诈证明（发现有欺诈后重复执行交易代码，来验证），另一种L2是zk证明，无需重复计算，但需要用zk的比较贵的GPU来生成证明，链上只是验证证明，而无需重复执行之前的交易转化函数代码。
早先的 @Polkadot 1.0 采用的是一种叫ELVES算法，不像ETH的欺诈算法，被动验证，而是采用概率类型的算法主动验证。@polkadot 2.0 时 验证集，已经被包装成一种叫Core的概念，core本质上是验证集中的子集，2.0支持Agile Coretime ，也就是动态使用core，1.0一个链只能用一个Core，2.0即将上线后支持Agile Coretime，也就是一个链根据需求可以动态使用coretime（验证子集数量），从而提升系统的服务负载。
那JAM则是在上面这些想法上基础演化，出现了这么多zk，op，智能合约，甚至普通的web2类无状态应用，是否能近一步抽象服务好适应这些不同的应用模型呢，并且让他们之间可组合交互。所以JAM是在这个基础之上近一步做了抽象。
- 各种不同的 L2/平行链的东西现在被称为 服务
- 区块/交易的东西现在被称为工作项或工作包
- 工作项属于服务，而工作包是一组工作项
- 服务由三个入口点描述，其中两个是 fn refine() 和 fn accumulated
- 这两个入口点的名称正是该协议被称为 JAM 的原因：连接累积机 (Join Accumulate Machine)。连接 (Join) 指的是 fn refine()，所有 Polkadot 核心都会为不同的服务并行执行大量工作。连接是指将数据提炼成一个较小的子集，然后传递到下一个阶段。
- 累积是指将上述所有操作的结果累积到主 JAM 状态
- 不同形态的服务被支持（op rollups，zkrollups，平行链，无状态应用，智能合约）
ETH时代是共享状态的单列状态机，
@polkadot 1.0 时代是可互操作的概率分片机。
@polkadot 2.0时代 是Agile Coretime 机。
JAM时代则是Join Accumulate Machine （JAM)
还有好多细节特性，这里只做了我理解到信息同步，更深入的了解为什么，JAM可以做到持续运行的程序，而无需通过交易来调起程序，这类特性未来和DEFI结合会产生出什么新模式产品？为什么JAM可以做到运行非状态类应用，比如JAM DOOM. 具体见视频：
学习资料：
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