Ethereum's Shanghai (April 2023) and Dencun (March 2024) upgrades introduced significant EVM changes. As the original EVM chain, Ethereum Classic actively monitors upstream improvements to evaluate which are beneficial for adoption — and which are irrelevant to a PoW chain.
Shanghai (April 2023)
Shanghai's primary feature was enabling staking withdrawals (EIP-4895), which is PoS-specific and irrelevant to ETC. However, Shanghai also included EVM improvements that ETC evaluates:
- EIP-3651 (Warm COINBASE): Reduces the gas cost of accessing the block producer's address. Relevant to ETC miners and contracts that interact with block.coinbase.
- EIP-3855 (PUSH0 instruction): Adds a new opcode that pushes zero onto the stack, reducing bytecode size and gas costs. A pure EVM improvement applicable to any chain.
- EIP-3860 (Limit and meter initcode): Caps the maximum size of contract initialization code and charges gas proportionally. Improves predictability of contract deployment costs.
ETC's Spiral upgrade (February 2024) adopted equivalent EVM improvements, keeping the execution environment aligned with upstream where changes are chain-agnostic.
Dencun (March 2024)
Dencun was primarily focused on Layer 2 scaling through blob transactions:
- EIP-4844 (Proto-danksharding): Introduced blob-carrying transactions designed for rollup data availability. This is L2-specific infrastructure with limited relevance to ETC, which operates as a standalone L1.
- EIP-1153 (Transient storage): Added TSTORE and TLOAD opcodes for storage that exists only during transaction execution, then is discarded. Useful for reentrancy locks and callback patterns — relevant to ETC smart contract development.
- EIP-5656 (MCOPY instruction): Added an efficient memory copy opcode, improving gas costs for memory-intensive operations. A pure EVM improvement.
- EIP-6780 (SELFDESTRUCT restriction): Limited the SELFDESTRUCT opcode to only send funds without deleting contract storage (unless called in the same transaction as creation). Improves state management predictability.
ETC's Evaluation Process
ETC does not automatically adopt Ethereum upgrades. Each EIP is evaluated independently through the ECIP process:
- PoS-specific changes (withdrawals, validator logic, blob transactions) are generally excluded
- Pure EVM improvements (new opcodes, gas schedule changes) are strong candidates for adoption
- Consensus changes are evaluated for PoW compatibility
- State management changes are reviewed for impact on ETC's state model
This selective approach allows ETC to benefit from the broader EVM ecosystem's development efforts while maintaining its distinct protocol characteristics.