Bitcoin Unlimited v0.12.1bu “Xpedited” -:- Official BU Release

Announcing BitcoinUnlimited version 0.12.1bu

The second official BU client release spotlights on-chain scaling by building upon Xthin with “Xpedited” which allows any full node owner to participate in a fast block relay sub-network by prior arrangement. This is of particular benefit to miners who require minimum latency in block propagation. This release is one of the last preparatory steps towards Bitcoin 1.x

BitcoinUnlimited v0.12.1bu highlights are:

BU v0.12.0 revised with Core v0.12.1 code-base changes plus


Xpedited block forwarding

  • Peer nodes can be pre-configured for single-hop Xthin block propagation
  • Faster block relay by removing handshake messaging

Xthin priority queue

  • A separate message queue is reserved for Xthin blocks so they can overtake any standard blocks and transactions pending processing by a node

Targeted bloom filters

  • Seeding the bloom filter for Xthin with a small subset of the memory pool where the set is based upon the most probable to-be-mined transactions

Enhanced statistics reporting

  • User settings for detailed node performance, transaction rates, standard / Xthin block processing and transmission information

Connection slot exhaustion mitigation

  • Denial of service protection against network crawlers which open multiple persistent connections

Bitnodes peer seeding

  • Obtain peer addresses from the public Bitnodes API
  • Enable users to specify custom DNS seed hosts
  • Update default DNS seed addresses using data from

Request manager

  • Preference logic to select Xthin and low latency nodes
  • Tracking of all sources of a block/tx and configurable timeouts result in retries

Miner settings for easy customizing

  • Block version via config param and command line
  • Get/Set coinbase string via config param and command line

Previously disabled in version 0.12.0:

  • Replace-by-Fee [commented out]
  • Alert Key [commented out]

Acknowledgements with special thanks for coding and testing:

Andrea Suisani
Andrew Stone
Peter Tschipper

Download location:
Source code:


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