In a blog post, Bitmain announced that it released the firmware for Antminer S9 to enable overt AsicBoost functionality. In the following week, Bitmain will release the same functionality for other BM1387-based models (R4, S9i, S9j, T9 and T9+).
AsicBoost is a mining optimization method that reduces the gate count on ASIC chips, which improves energy consumption and pushes down system costs. As opposed to covert AsicBoost, overt AsicBoost modifies version field in the block header, which makes it easily detectable. The method was invented in 2016 by Timo Hanke, Director of Engineering at DFINITY, in collaboration with Sergio Lerner, Chief Scientist at RSK Labs.
Bitmain initially decided against activating overt AsicBoost because of the legal uncertainty. Since early March, AsicBoost is available for licensing under the Blockchain Defensive Patent License (BDPL), a defensive patent initiative. Bitmain said that the company "continues to respect third parties’ IP right and take actions accordingly. Based on legal opinions from various jurisdictions, we believe that there isn’t and may never be a patent right over AsicBoost. Thus, all miners should be entitled to make their own choice on whether to use AsicBoost technology without anybody having an exclusive right over it."