BM1391

BM1391 is Bitmain's 7 nm SHA-256 mining ASIC, introduced in 2018 as a refinement of the Antminer S9 generation rather than a clean-sheet design. Although it is usually listed under its own model name, the runtime keys it on the shared silicon command surface 0x1387 — the same register interface as the S9-era BM1387 — which makes it register-compatible with that earlier chip rather than a separate dispatch identity. Like every die in the Antminer lineage, it computes the double-SHA-256 hashes that secure Bitcoin's proof-of-work.

Where the BM1391 is used

The BM1391 is the die behind Bitmain's first wave of 7 nm consumer miners: the Antminer S15 and its lower-binned sibling, the T15. Some firmware corpora and parts catalogs also fold the chip under the S9 SE, reflecting how closely the S15/T15 platform descends from the S9. The S15/T15 host attribution is the curated-reference consensus; treat any S9 SE labeling as the same underlying silicon family rather than a different chip.

What the silicon looks like

On a BM1391 hashboard, 72 chips are wired in a serial chain and grouped into 12 voltage domains of 6 chips each, so the control board manages current across small groups rather than one chip at a time. Each domain runs at roughly 1.53 V. A single BM1391 die delivers on the order of 111 GH/s, and at the chip's nameplate operating point its parent miner reaches an efficiency near 57 J/TH — a large step over the ~98 J/TH of the 16 nm BM1387 it descends from, and the headline reason Bitmain moved the S9 architecture onto a 7 nm process.

Power, efficiency, and platform

At its factory rating, a BM1391-based S15 lands near 28 TH/s while drawing roughly 1,600 W, which works back to the ~57 J/TH figure above; the T15 trades a little hashrate for a slightly higher draw. Because the design predates Bitmain's on-chip version rolling — the hardware ASICBoost technique that first appeared in the later BM1362/BM1366/BM1368 family — the host control board still shoulders more of the job-management work than it does on S19/S21-class chips. The S15 also rides the same Xilinx Zynq 7010 control platform (dual Cortex-A9 at 667 MHz) used by the S9 and S17, underlining that the BM1391 is an evolution of that ecosystem rather than a break from it.

Why it matters for repair and diagnostics

For anyone servicing an S15 or T15, the shared 0x1387 identity is the key fact: diagnostic tools and drivers see the chain as a BM1387-class device and read the same chip ID back, so S9-era test fixtures and chip-detection routines apply directly. Because voltage is set per domain rather than per chip, a fault usually surfaces as an entire six-chip domain dropping out, which narrows where to probe on a dead hashboard. Two cautions follow from the chip's lineage. First, do not mix BM1391 boards with BM1387 boards in one miner without re-confirming the per-model frequency table — register compatibility does not guarantee a matching clock profile. Second, although the BM1391 is cloned less often than the BM1387, the same counterfeit discipline applies: verify the chip-ID readback and board geometry rather than trusting a silk-screen mark.

Why it matters for miners

The BM1391 marks the moment Bitmain carried its proven S9 / BM1387 ASIC chip design onto a 7 nm node, nearly halving energy per hash without redesigning the core hashing logic. Understanding its 0x1387 lineage, 72-chip chain, and 12-domain layout helps you reason about S15/T15 efficiency, plan hashboard-level repairs, and recognize that much of what you already know about servicing an S9 transfers to these machines. For how this older die compares with the current-generation BM1368 and the rest of the SHA-256 lineup, our miner catalog lays the families out side by side so you can place the S15/T15 in context before buying or repairing one.