Firmware & Recovery

Firmware Compared (Stock vs Custom)

Five firmware families a Miner Technician may encounter, what each one costs and changes, and why a fresh flash ramps instead of jumping to full hashrate.

The five families

Every miner on the floor runs one of five firmware families. Stock ships from the factory. The other four are custom flashes that trade a small dev fee for tuning and efficiency. Know which is which before you touch a board.

Firmware	Dev fee	Warranty	Tuning / Notes
Stock (Bitmain/MicroBT)	0%	Intact	Conservative fixed profiles, minimal tuning
Braiins OS+	2-2.5% (0% on Braiins Pool)	Void	Per-chip autotune, native Stratum V2, Antminer-focused
VNish	2-2.8%	Void	Aggressive overclock, broadest Antminer support, very common
LuxOS	2.8% (0% on Luxor Pool)	Void	Autotune + curtailment; Antminer plus select Whatsminer
ePIC	AltairOS 2.2% / UMC OS 1.5%	Void	Perpetual Tune autotuner; AltairOS on stock board, UMC OS on swap-in UMC board

All custom firmware VOIDS the Bitmain/MicroBT warranty. All of it is reversible - reflash stock to restore the factory image before any RMA.

The two ePIC products

ePIC is not one firmware. It is two, and the difference is which control board they run on.

AltairOS (2.2%) - software that installs onto the existing stock control board.
UMC OS (1.5%) - runs on the UMC replacement control board you swap in when the stock controller is dead or locked.
Reach for UMC OS when the factory controller will not boot; AltairOS when the board is healthy and you just want tuning.

What firmware actually changes

Firmware sets clock FREQUENCY per individual chip. It regulates VOLTAGE per voltage-domain - a group of chips sharing one DC-DC converter. No firmware can set per-chip voltage.

Frequency: tuned chip by chip, so a weak chip can be clocked down on its own.
Voltage: set for the whole domain at once - every chip on that converter gets the same rail.
Result: one weak chip drags its entire domain, and you cannot fix it with voltage without overshooting every healthy chip next to it.

You cannot chase a single bad chip with voltage. Chips share a DC-DC converter, so raising the domain to save one weak chip overvolts the healthy ones beside it.

Why a fresh flash ramps, not jumps

Autotune sweeps toward a power-target or hashrate-target and keeps re-tuning over HOURS. Braiins says let it run 12-24h. It re-tunes again after any restart or coolant/ambient shift.

A freshly flashed miner RAMPS toward target - it does not jump to full hashrate.
Restart the miner, or move it to colder/warmer air or a coolant change, and the autotuner starts sweeping again.
Low hashrate in the first hours after a flash is the tuner working, not a hardware fault.

Do not mistake a still-tuning board for a fault. Give a fresh flash 12-24h to settle before you chase low hashrate or pull the board for RMA.

Dev fee mechanics and true cost

A dev fee is not a cash invoice. It is skimmed production - the miner mines to the developer's pool for a small slice of time and hashrate.

Pool-tied: Braiins and LuxOS waive or offset the fee when you mine on their own pool (Braiins Pool, Luxor Pool).
Universal skim: VNish takes its slice on any pool you point it at.
The fee shows up as a few minutes of your hashrate donated, not a line on a bill.

True cost = dev fee + pool fee - the ~10-15% efficiency gain custom firmware typically delivers. The efficiency gain usually outweighs the skim, which is why the floor runs custom.