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Antminer S21 Pro Underclock

There is no real underclock table for the Antminer S21 Pro — and pages showing exact settings for it are guessing. No usable extraction preset set exists for this model: no extraction set exists for it anywhere in the source catalog. This page explains what that means, the watt-target method that works without a published envelope, and what we can actually verify.

Antminer S21 Pro — tuning envelope Unknown

No extraction data exists for the S21 Pro in the source catalog. Manufacturer stock rating only; no tuning envelope is published.

The honest way to tune this model today: set a watt target in your firmware and let the autotuner derive frequency and voltage for your unit. That method needs no published envelope — it is the whole point of autotuning firmware. Pages showing exact “underclock settings” for this model are publishing stock-spec numbers or another SKU's data; when a set for this unit clears source-integrity checks, its envelope will appear here with a status.

For what this chip generation does in the models we can verify, see the generation efficiency bands on the index — context only, never a claim about this SKU.

Set the target in your firmware

Circuit math vs. PSU reality: the 1,440 W / 1,920 W lines are the continuous-load limits of 120 V 15 A / 20 A circuits (80% of breaker rating, per NEC continuous-load practice). Wattage fit alone does not make a 120 V miner: stock Bitmain APW-series supplies of the S17/S19/S21 generations accept 200–240 V input only, so a 120 V build is a PSU-level project regardless of watt target.

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.

Antminer S21 Pro full specifications → · Family / firmware hub → · Row-level operating points (source dataset) → · All tuning envelopes →

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Last reviewed August 13, 2026.