BM1397

BM1397 is Bitmain's 7 nm SHA-256 mining ASIC (silicon chip ID 0x1397), the second-generation die introduced in 2019 that powers the air-cooled Antminer S17 and T17 line — base, Pro, and Plus models. It computes the double-SHA-256 hashes that Bitcoin's proof-of-work depends on, and it consolidated Bitmain's move to 7 nm silicon — begun a year earlier with the S15's BM1391 — leaving the 16 nm S9 era behind.

Where the BM1397 is used

The BM1397 is the production driver for the S17/T17 base, Pro, and Plus line. The same die sits inside the S17, the S17 Pro, the T17, the S17+, and the T17+. Across all five models, only the firmware tuning targets and bin grades differ; the underlying silicon is the same 7 nm chip carrying the 0x1397 ID.

Two persistent mistakes are worth clearing up, because both are widespread in marketplace listings and even in repair notes. First, older references sometimes credit the S17 generation to a "BM1393." That is incorrect: BM1393 is a named-only variant from the S9 family (S9j / S9k / S9 SE), and it never shipped in an S17. Second — and this is the one that costs people money — the S17+ and T17+ are routinely attributed to the closely related BM1396. They are not BM1396 machines: the "Plus" boards run the BM1397 like the rest of the line. The BM1396 (0x1396) is the die of the S17e and T17e "e" variants only. The two chips share the same 0x51/0x41 command-header family and are register-compatible, but they are distinct silicon with distinct chip IDs — firmware dispatches on the chip's address word, and a board from one family should never be cross-populated onto the other in a repair.

What the silicon looks like

Each BM1397 contains roughly 672 hashing cores and communicates over the standard Bitmain serial chain using the 0x51/0x41 command-header protocol. On a stock S17 hashboard, 48 BM1397 chips are wired in a single serial string, and the board is divided into 12 voltage domains of 4 chips each. Each domain runs at roughly 1.55 V, with the domains stacked in series so the control board manages current across groups of four chips rather than one chip at a time. A complete S17 carries three of these boards driven by a Xilinx Zynq-7010 control board.

Power, efficiency, and tuning

Per-chip throughput lands in the ~166–200 GH/s range depending on model and clock, and wall-plug efficiency spans roughly 40–55 J/TH across the generation — the S17+ sits near 40 J/TH, the base S17 around 45 J/TH, and the T17 closer to 55 J/TH. Because the chip exposes a tunable PLL frequency and a per-domain voltage, custom firmware can walk these operating points to chase efficiency, peak hashrate, or a fixed power envelope. The S17 generation arrived just as autotuning firmware matured, so much of the practical efficiency on these boards comes from runtime frequency/voltage curves rather than fixed factory presets.

S17-generation chip identification at a glance

• 0x1397 — BM1397: Antminer S17, S17 Pro, T17, S17+, T17+
• 0x1396 — BM1396: Antminer S17e and T17e only
• BM1393: a named-only S9-family variant (S9j / S9k / S9 SE) — never an S17 chip

When in doubt, read the chip ID back from the chain before ordering parts or matching a donor board. The ID, not the sticker or the listing, is the truth — and because BM1396 and BM1397 answer on the same header family, a board can talk to your tools while still being the wrong board for the machine in front of you.

Why it matters for repair and diagnostics

The BM1397 is one of the most thoroughly studied mining ASIC chips, with openly documented register behavior (the Mujina reverse-engineering work covers this family in detail), which makes board-level diagnostics on S17 hardware unusually approachable. That openness matters because the S17 generation was notorious for thermal-stress failures: cracked solder joints, dead domains, and chips that pass a quick power-on but fail under sustained load. Harvested BM1397 dies are also among the most heavily recycled on the used market, so a board advertised as "tested working" still warrants a full bench check — verify every domain's voltage, look for a chip count short of 48 on the chain, and confirm the hashboard holds rate under thermal load before trusting it.

In practical terms, the BM1397 is the chip you are servicing whenever you open an S17- or T17-class Antminer other than the "e" variants. Knowing its 48-chip chain, 12-domain layout, and per-domain voltage lets you reason about a dead or under-hashing board at the domain level instead of guessing. For the full chip-to-model map across every generation, see our ASIC chip reference; the BM1368 entry covers the current S21-generation silicon, and our miner catalog lays out where each chip generation lands across the Antminer family.