Bitmain has released a new firmware update for its Antminer series, disabling the control board's microUSB port. This update affects several Bitcoin ASIC models, including the S19k Pro, S21, and S21 Pro, with the change first noted on the S21 XP. The microUSB port was previously utilized for flashing third-party firmware and system recovery, and its deactivation significantly complicates maintenance and restricts miners' ability to optimize performance and power efficiency independently.