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Advanced share difficulty features

2014-06-17 18:36 UTC

Two new extensions to the Stratum protocol are now available on all our servers: suggest_difficulty and suggest_target. Both extensions serve the same purpose: to allow mining clients to suggest an ideal share difficulty upon connection. This is especially useful for very fast ASIC miners, as it allows them to avoid bursts of shares right after a connection to the server is established. This functionality is currently only supported by BFGminer, but we expect more mining software to adopt it in the future.

Another feature has also been introduced which allows miners to set a fixed difficulty, overriding the default adaptive mechanism. This is of course totally unneeded under normal conditions, as the pool is capable of automatically serving work of optimal difficulty. This feature is mainly intended for miners that have no choice but using defective software or hardware that only works correctly within certain difficulty ranges. The feature is enabled per-connection, by appending the string “,d=N” to the worker's password. For example, if a worker's password is “foo”, connecting with password “foo,d=64” will ask for share difficulty 64. Keep in mind that difficulty can only be set per-connection, so if you connect multiple workers via a proxy they will all share the same difficulty (this is a limitation of the Stratum protocol). Moreover, the server may round and/or cap the difficulty you asked for in order to prevent denial-of-service attacks.