Definition
SD card flashing is a recovery technique for ASIC miners whose control board will no longer boot from its internal storage. You write a firmware image to a microSD card, insert it into the control board, and power on; the board boots from the card instead of its on-board flash. From there you can either keep running off the card or use it to rewrite the internal storage and restore permanent operation. It is the workhorse method for rescuing a unit after a failed update.
When it is the right tool
Reach for SD card recovery whenever a miner is dark after a firmware flashing attempt, when the miner web UI never comes up, or when the on-board image is corrupted. In the large majority of these cases the SD method brings the board back. A true hard brick that even SD recovery cannot fix is rare and usually points to a hardware fault such as a damaged flash chip or bootloader.
Practical notes
Use a small-capacity card; cards under 16 GB are recommended because larger ones are more error-prone in this role. Match the image to your exact control board revision, since flashing an image built for a different board is a common cause of failure. Write the image with a verified imaging tool and confirm the write completed before inserting the card.
For model-specific procedures, see our SD card firmware recovery guide and the broader firmware reference.
In Simple Terms
SD card flashing is a recovery technique for ASIC miners whose control board will no longer boot from its internal storage. You write a firmware…