Antminer S19j Pro+ Underclock
The honest answer to “S19j Pro+ underclock settings”: set a watt target of 1,450 W — the deepest floor of the air-cooled S19 family in the catalog, and also its best-efficiency point (22.3 J/TH). On a rising curve like this one, underclocking is not a compromise — it is the optimum. No frequency or voltage to copy; the autotuner derives both.
Quick answer
The Antminer S19j Pro+ tunes across a 1,450–5,900 W envelope (Normal mode: 65–159 TH/s). Best catalog efficiency is 22.3 J/TH, and the sweet spot — everything within 5% of it — spans 1,450–1,750 W. The floor is 1,450 W — 43% of the 3,355 W factory rating. There are no frequency/voltage settings to copy: you set a watt target and the firmware autotuner derives the rest for your unit. Status: Verified (extraction).
Best efficiency sits at or near the envelope floor: the lowest watt target your hashrate goal tolerates is also the most efficient point in the catalog.
Antminer S19j Pro+ — Normal mode Verified (extraction)
Floor fits a 120 V 20 A continuous-load budget (1,920 W) but not 15 A. Budgets are the NEC 80% continuous-load rule; circuit fit only — stock Bitmain APW-series PSUs require 200–240 V input, so any 120 V build needs a PSU change regardless of watt target. At the floor this mode dissipates about 4,947 BTU/h (watts × 3.412).
Source: Firmware-extraction set.
How to set a power target on this model
Aftermarket firmware exposes underclocking as a power target (sometimes "power limit" or a preset picker), not as frequency/voltage fields. Pick a watt figure inside the envelope above; the autotuner benchmarks your boards and settles onto it over a tuning period. Braiins OS+, VNish and LuxOS each expose this in their own UI, and DCENT_OS uses watt-target autotuning on its supported models; the undervolting guide walks through the firmware side step by step, and the firmware comparison covers which firmware supports which model. Verify the result at the wall with a meter — the target is an input, the wall draw is the fact.
- Braiins OS+ — set a power target →
- VNish — pick a preset →
- Stock firmware modes →
- LuxOS power targeting →
Frequency and voltage are calculated at runtime by the firmware autotuner — never fixed presets; per-unit silicon quality, ambient temperature and cooling shift real results.
These envelopes are derived aggregates (bounds, bands, counts) — the row-level operating points, the interactive picker and the CSV/JSON of the source data live in the ASIC Power Profiles Database, the single source dataset for every number on this page.
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Last reviewed August 13, 2026.