ECIP 1089: Phoenix EVM and Protocol Upgrades (Classic Option) Source

Author/raw PONG _GHMoaCXLT

Simple Summary

Enable the outstanding Ethereum Foundation Istanbul network protocol upgrades on the Ethereum Classic network in a hard-fork code-named Phoenix to enable maximum compatibility across these networks.

This is the classic option equaling to an Istanbul option without gas repricing.


Add support for a subset of protocol-impacting changes introduced in the Ethereum Foundation (ETH) network via the Istanbul hardforks. The proposed changes for Ethereum Classic’s Phoenix upgrade include:

  • Add Blake2 compression function F precompile
  • Reduce alt_bn128 precompile gas costs
  • Net gas metering for SSTORE without dirty maps
  • Add ChainID opcode
  • Disable SSTORE with gasleft lower than call stipend
  • Calldata gas cost reduction
  • Add SELFBALANCE opcode

This document proposes the following blocks at which to implement these changes in the Classic networks:

  • 999_983 on Mordor Classic PoW-testnet (April, 2020)
  • 2_200_013 on Kotti Classic PoA-testnet (April, 2020)
  • 10_500_839 on Ethereum Classic PoW-mainnet (June 10th, 2020)

For more information on the opcodes and their respective EIPs and implementations, please see the Specification section of this document.


To enhance the Ethereum Virtual Machine’s (EVM) capabilities, various opcodes shall be added to the Ethereum Classic networks, all of which have been in use on the Ethereum Foundation networks since end of 2019.


Technical specifications for each EIP can be found at those documents respectively:

  • EIP-152: Add Blake2 compression function F precompile
  • EIP-1108: Reduce alt_bn128 precompile gas costs
  • EIP-1283: Net gas metering for SSTORE without dirty maps
  • EIP-1344: Add ChainID opcode
  • EIP-1706: Disable SSTORE with gasleft lower than call stipend
  • EIP-2028: Calldata gas cost reduction
  • ECIP-1080: Add SELFBALANCE opcode


Interoperability: Establishing and maintaining interoperable behavior between Ethereum clients is essential for developers and end-user adoption, yielding benefits for all participating chains (e.g., ETH and ETC, Ropsten and Mordor, Görli and Kotti).

Immutability: None of the introduced new opcodes in the EVM has the potential to change the behavior of existing contracts; in the case where previously an arbitrary invalid bytecode would have been deployed to the network, none of them would be able to modify the state of the Ethereum Classic networks retrospectively. Adding opcodes to the EVM increases its functionality and should be considered a feature upgrade rather than a modification.


Adoption of the content of this ECIP requires a hard fork as it introduces changes that are not backward compatible.

The following clients with Ethereum Classic support implement the Istanbul features currently and would be able to support the Phoenix upgrade:

  • Hyperledger Besu
  • Core-Geth
  • Multi-Geth
  • Parity Ethereum

Final Note

Both, the Geth Classic client and the Morden testnet will no longer be supported by the community and not recieve the Phoenix ugrades.

  • Users of the Geth Classic client are urged to migrate their services to Parity Ethereum, Multi-Geth, or Hyperledger Besu. It is no longer recommended to run Geth Classic in production.
  • Users of the Morden Classic testnet are urged to migrate their applications to the Kotti Classic or Morder Classic testnets.

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