Bitcoin Mining Controllers Can Waste Energy Despite Reduced Hashrate
A recent analysis by Eric Price has highlighted a potential issue in Bitcoin's mining process. Specifically, some variable-difficulty controllers can continue to demand work from miners even after they've reduced their hashrate. This can lead to wasted energy and resources as the miner continues to consume electricity without producing any new shares.
The problem occurs when a pool assigns each connection a share difficulty that's easier than Bitcoin's block difficulty. If the controller recalculates only when a share arrives, it can become stuck on an old assignment, making it less likely for subsequent shares to be accepted. This can lead to a sparse stream of shares.
A testable controller weakness has been identified in some pool-assigned share difficulty controllers. The issue is not unique to Bitcoin's network difficulty and only affects specific variable-difficulty controllers. A timer-triggered recovery mechanism is already implemented in the Stratum V2 reference implementation, which avoids a permanent freeze by recalculating on a timer.
The analysis suggests that operators can now test this behavior directly using MARA Foundation's open-source shape-proxy. By testing different profiles, such as step, ramp, and stall, it's possible to see whether the controller recovers or remains stuck. A falling assigned difficulty indicates recovery, while a pinned target shows slow or absent recovery.