Difference between Low Power Mode and Low Power Enhanced Mode

Low Power Mode (LPM) trims wattage while holding hashrate roughly steady; Low Power Enhanced Mode drives the chip clock down much harder, so it sheds a large chunk of both hashrate and power. Both are firmware-level modes exposed by Bitmain’s LPM firmware builds for the Antminer S9, S9i, and S9j. Neither is an overclock — they are the opposite: controlled under-clocking of the BM1387 ASICs to move the machine to a lower, more efficient operating point. This guide explains what each mode actually does to the hardware, how to select it, and how to choose between them.

What the modes do under the hood

An S9 hashboard carries 63 BM1387 chips wired as 21 series voltage domains (three chips per domain). Voltage is set per domain by the PSU feeding the board — there is no per-chip voltage control on this platform. What the LPM firmware changes is the PLL clock frequency the chips run at. Lower frequency means fewer hash cores toggling per second, which lowers both the delivered terahashes and the switching power the board draws. That single lever — frequency — is what separates the three modes:

• Normal Mode: stock frequency. Full hashrate, full power.
• Low Power Mode: a modest frequency reduction. Hashrate barely moves; power drops meaningfully. This is the efficiency sweet spot.
• Low Power Enhanced Mode: a much deeper frequency cut. Absolute hashrate falls sharply and power falls with it — the mode for the lowest possible wattage, not the best efficiency.

The three S9 firmware files

Bitmain shipped LPM as separate firmware images rather than a runtime toggle on the original builds. Using the S9 auto-frequency line as the example, three images exist:

• ANTMINER-S9-all-...-autofreq-user-Update2UBI-NF.tar.gz — the original stock firmware (Normal Mode only).
• ANTMINER-S9-LPM-20181102.tar.gz — the Low Power Mode firmware: lowers power while holding hashrate.
• ANTMINER-S9-all-201812051512-autofreq-...-NF.tar.gz — the later image that exposes both LPM and Enhanced Mode via checkboxes and can lower hashrate as well as power.

Only flash official Bitmain firmware pulled from the manufacturer’s own support portal. Do not source these images from random forum re-uploads — a tampered S9 image is a well-known malware vector. If you cannot obtain the file cleanly, do not proceed.

Selecting a mode after flashing

Once the later firmware is installed, the miner configuration page presents two checkboxes. They map to the modes as follows:

• Normal Mode: neither box checked.
• Low Power Mode: only the first box checked.
• Low Power Enhanced Mode: the second box checked (or both boxes checked).

Apply the setting, let the miner reboot, and give it 15–30 minutes to settle before you trust the reported figures — the S9 ramps and self-tunes on the way up.

Reference figures

These are Bitmain’s published reference numbers for one representative S9 (nominal 13.5T class). Treat them as illustrative, not guaranteed — real output shifts with ambient temperature, PSU, chip quality, and board wear:

The efficiency column (watts divided by terahashes) exposes the real trade-off: Low Power Mode is the most efficient of the three — it drops ~200 W for only ~0.3 TH/s. Enhanced Mode is not more efficient than LPM; you give up ~30% of hashrate to reach the lowest absolute draw. Enhanced Mode earns its keep only when your ceiling is total wattage (a heat budget, a shared circuit, a small solar/battery bank), not sats per joule.

For watt-level context beyond the S9’s modes, the S9 underclock reference and the full envelope database show what each family supports.

How to choose

1. Chasing efficiency / lower power bills: run Low Power Mode. You keep nearly all the hashrate and cut roughly 200 W per unit.
2. Hard wattage or thermal cap: use Enhanced Mode when a breaker, PSU headroom, or a heat-reuse target forces the lowest possible draw and you accept the hashrate hit.
3. Cheap or free power and you want maximum sats: stay on Normal Mode — efficiency matters less than raw output.

Run the arithmetic against your own electricity rate and the current network difficulty before committing — the goal is ROI, and the right answer changes with the power price. The S9’s PSU (APW3++ class) runs fine on 110/120 V at reduced output, so North American home operators can host these on standard circuits.

Stability, safety, and common mistakes

• If hashrate drops off, chips drop out, or the board hunts: back off — disable LPM or flash back to the original firmware. Aggressive under-clocking occasionally destabilizes marginal boards. Instability under LPM often exposes a board that was already weak; run the machine through the ASIC fault finder before blaming the mode.
• Do not flash across the wrong model. An S9 image on an S9j (or vice versa) will misbehave — match the firmware to the exact model.
• Power discipline while working inside the unit: the S9’s low-voltage DC hashboard supply is not a shock hazard, but the PSU’s internal mains-side capacitors hold a lethal charge (hundreds of volts). Unplug and let the PSU sit before opening it — never probe a live supply.
• Don’t expect miracles from old silicon. LPM improves efficiency but a well-worn S9 is still a ~90–100 J/TH machine; it will never match a modern rig on sats-per-joule.

If a board still won’t hold a mode after a clean reflash, the fault is hardware, not configuration — that is a repair job, not a firmware one.

Related: Confirm your model and firmware line against the Antminer manuals, brush up on joules per terahash and mining firmware in the glossary, and if a board keeps dropping under LPM, start a repair with us.