---

name: bitcoin-mining-firmware description: | ASIC mining firmware: Braiins OS+, Vnish, BUMa, ESP-Miner/AxeOS (Bitaxe), stock firmware, custom firmware tradeoffs. Overclocking, undervolting, autotuning, efficiency curves. USE WHEN: deploying mining firmware, evaluating efficiency vs hashrate, choosing custom vs stock. allowed-tools: Read, Grep, Glob

ASIC Firmware

ASIC manufacturers ship stock firmware (BMMiner, etc.). Custom firmware (Braiins OS+, Vnish, BUMa) often improves efficiency, adds features, or enables Stratum V2. Open-source hardware (the Bitaxe family) instead ships open firmware from the start: ESP-Miner / AxeOS.

Stock firmware

• Bitmain: BMMiner / Antminer firmware.
• MicroBT: Whatsminer firmware.
• Canaan: AvalonMiner firmware.

Pros: works out of box, manufacturer support. Cons: limited tuning, possibly built-in backdoors / mining for manufacturer's pool, no SV2.

Braiins OS+

Open-source firmware by Braiins (Slush Pool team):

• Compatible with: Antminer S9, S17, S19 series, others.
• Adds: Stratum V2, autotuning, dashboard, monitoring.
• Open-source (auditable).
• Free for personal use; pool fee discount with Braiins.

Vnish (closed-source)

• Popular firmware especially for S19 series.
• Aggressive tuning profiles.
• Closed-source; some controversy about backdoors.
• Paid license for some models.

ESP-Miner / AxeOS (Bitaxe)

Firmware for the Bitaxe family of fully open-source, single-chip (or few-chip) ASIC boards. These are real SHA-256 ASICs in the sub-TH/s to few-TH/s range, not the ESP32 KH/s class below.

Hardware (design files at github.com/bitaxeorg, as of September 2026):

Board	ASIC	Harvested from	Vendor efficiency claim
Max	BM1397	Antminer S17	-
Ultra	BM1366	Antminer S19 XP	0.021 J/GH (21 J/TH)
Supra	BM1368	Antminer S21	17.5 J/TH
Gamma	BM1370	Antminer S21 Pro	15 J/TH
Gamma Turbo (GT)	2x BM1370	Antminer S21 Pro	-
Gamma Hex	6x BM1370	Antminer S21 Pro	-

A single Gamma carries one of the 195 BM1370s in an S21 Pro, so roughly 234 / 195 ≈ 1.2 TH/s per board off a 5 V barrel jack (PSU must sustain >4 A; 25-30 W recommended).

Firmware: ESP-Miner, ESP32-S3 firmware whose web UI is called AxeOS, maintained by Open Source Miners United (OSMU) at github.com/bitaxeorg/ESP-Miner. Latest release v2.15.1 (29 August 2026).

• Stratum V1 native, with optional per-pool TLS (tls_mode, custom CA cert) - so solo pools can be reached over an encrypted socket.
• Stratum V2 support landed in v2.14.0 (June 2026) and was extended in v2.15.0 (August 2026): 8 KiB SV2 frames, per-pool "require authentication", fractional SV2 difficulty, pending-share display.
• Wi-Fi + browser config; no host computer. REST API at /api/system/info, /api/system/asic, /api/system/statistics, plus a /api/ws log stream.
• Flash via pip install bitaxetool or the Bitaxe Web Flasher. Since v2.15.0 AxeOS is embedded in esp-miner.bin - no separate www.bin upload.
• Per-board frequency/voltage are user-set; benchmark scripts rather than a built-in autotuner are the usual way to find the J/TH knee.

Why it matters: these boards make solo mining a home appliance. On 10 July 2026 a solo miner on Public Pool found block 957,382 (coinbase tagged Public-Pool, single 3.138 BTC payout); it was widely reported as a Bitaxe.

BUMa / NerdMiner (ESP32 class)

• Custom firmware for NerdMiner (low-power solo-mining device).
• ESP32-based, small hashrate (KH/s range) - the microcontroller itself hashes; there is no ASIC.
• Educational / hobby / lottery use. Distinct from the Bitaxe boards above, which are ASIC hardware six-plus orders of magnitude faster.
• Related ASIC forks: NerdQAxe / NerdQAxe+ run a fork of ESP-Miner (shufps/ESP-Miner-NerdQAxePlus), not NerdMiner firmware.

Tuning concepts

Overclocking

Increase chip frequency above factory spec. Hashrate up, electricity up, more heat, may shorten ASIC lifespan.

Undervolting

Lower voltage at same frequency. Electricity down, slight hashrate loss, longer lifespan.

Autotuning

Firmware automatically adjusts per-chip parameters to find optimum J/TH (joules per terahash). Sometimes 10-20% efficiency gain over stock.

Common bugs

• Aggressive overclock → hardware errors → rejected shares → less income than conservative tune.
• Cooling not matching new heat profile → throttling.
• Pool config left as factory's pool → unintended donations.
• Bitaxe flashed with the wrong board-version image (e.g. a 401 image on a 6xx Gamma) → wrong voltage/frequency defaults.

See also

• pow/SKILL.md
• stratum-v2/SKILL.md
• pool-architectures/SKILL.md
• decentralized-pools/SKILL.md