Definition
The BM1366 is a SHA-256 mining ASIC from Bitmain, built on a TSMC 5 nm process and belonging to the same generation of “full-header” chips as the BM1368 and BM1370. It is the silicon at the heart of the Antminer S19 XP and S19k Pro, and it has become the most accessible industrial-grade ASIC in the open-source mining community because a single unit also powers small solo-mining devices.
Where the BM1366 lives
In Bitmain’s lineup the BM1366 hashes inside several hosts. The S19k Pro packs 77 chips per board (11 voltage domains of 7 chips), with a factory nameplate of roughly 605 MHz, 13.8 V, and about 120 TH/s at the wall. The higher-binned S19 XP uses the same chip at a denser layout — 110 chips per board (11 domains of 10) — to reach a higher throughput. The same silicon also appears in the S19j XP and the hydro-cooled S19 XP Hydro variants. Outside the industrial fleet, a single BM1366 is the engine of the open-source Bitaxe Ultra, and six of them run side by side in the Bitaxe Hex Supra for a higher combined hashrate at home-friendly power levels.
One detail worth knowing for repair and firmware work: although early documentation tied the BM1366 to a single control-board family, the chip is genuinely carrier-agnostic. Industrial BM1366 boards ship on Xilinx Zynq, Amlogic, and CVitek SoCs, and they are NoPic designs — there is no separate PIC voltage-controller microcontroller on the hashboard. The BHB56902 (S19k Pro) and BHB56802 (S19 XP) hashboards are distinguished by their per-domain chip count rather than by their host processor.
How the BM1366 actually works
The BM1366 represents a real architectural shift from the older S17/S19-class ASIC chips like the BM1398. Instead of the host computing midstates and streaming them to the chip, the BM1366 receives an 82-byte full block header over its UART and computes the SHA-256 midstate internally. This simplifies the work-dispatch path and is part of why the chip pairs so cleanly with a low-cost ESP32 controller in the Bitaxe rather than needing a full FPGA.
It also performs hardware version rolling for AsicBoost on-chip. A version-rolling register enables the chip to iterate the block-header version bits (the BIP320 mask covering the configurable range) entirely in silicon, expanding the search space without the pool or host having to enumerate those headers. A practical consequence for firmware authors: the chip rolls those bits whether or not a pool negotiated version rolling, so the share-submission path must reconstruct the rolled version it actually hashed — otherwise the vast majority of valid work gets silently discarded. This is one of the load-bearing lessons the open-source firmware community has had to relearn the hard way.
Voltage delivery differs by host. On industrial S19 XP / S19k Pro boards the chips sit in series-stacked domains fed from the board rail, while the Bitaxe drives a single chip from a TPS546 buck regulator at roughly 1.2 V. Because every chip in a domain shares current, a single weak BM1366 can drag down its whole domain — a recurring theme in ASIC troubleshooting when a board posts a partial hashrate or fails a chip count.
Why the BM1366 matters for miners
For an operator, the BM1366 is the dividing line between “legacy 5 nm efficient” and the current 3 nm generation. It is meaningfully more efficient than the 7 nm BM139x chips that came before it, yet it is widely available on the secondary market as S19 XP and S19k Pro units age out of large hashcenters. That combination — proven silicon, large installed base, repairable boards — makes BM1366 hardware a sweet spot for home miners and small operations who want strong efficiency (J/TH) without paying flagship prices.
It is also the most approachable on-ramp to running your own node-and-miner stack. A single BM1366 on a Bitaxe lets you solo mine, learn the Stratum and chip-init internals, and keep one more layer of the network decentralized — all from a device that fits on a desk. The same chip knowledge transfers directly up to a full S19 XP, so what you learn on a single-chip Bitaxe applies at 140 TH/s.
If you are sourcing BM1366 hardware — whether a fully built S19 XP for a heated workshop or a single-chip board to learn on — D-Central stocks both industrial Antminers and open-source kits. Browse the miners catalog or the open-source mining gear to find a BM1366 platform that fits your power budget and your sovereignty goals.
In Simple Terms
A Bitmain mining chip powering the Antminer S19 XP and Bitaxe Supra. Efficient at around 21.5 J/TH.
The BM1366 is a SHA-256 mining ASIC from Bitmain, built on a TSMC 5 nm process and belonging to the same generation of "full-header" chips as the BM1368 and BM1370. It is the silicon at the heart of the Antminer S19 XP and S19k Pro, and it has become the most accessible industrial-grade ASIC in the open-source mining community because a single unit also powers small solo-mining devices.
Where the BM1366 lives
In Bitmain's lineup the BM1366 hashes inside several hosts. The S19k Pro packs 77 chips per board (11 voltage domains of 7 chips), with a factory nameplate of roughly 605 MHz, 13.8 V, and about 120 TH/s at the wall. The higher-binned S19 XP uses the same chip at a denser layout — 110 chips per board (11 domains of 10) — to reach a higher throughput. The same silicon also appears in the S19j XP and the hydro-cooled S19 XP Hydro variants. Outside the industrial fleet, a single BM1366 is the engine of the open-source Bitaxe Ultra, and six of them run side by side in the Bitaxe Hex Supra for a higher combined hashrate at home-friendly power levels.
One detail worth knowing for repair and firmware work: although early documentation tied the BM1366 to a single control-board family, the chip is genuinely carrier-agnostic. Industrial BM1366 boards ship on Xilinx Zynq, Amlogic, and CVitek SoCs, and they are NoPic designs — there is no separate PIC voltage-controller microcontroller on the hashboard. The BHB56902 (S19k Pro) and BHB56802 (S19 XP) hashboards are distinguished by their per-domain chip count rather than by their host processor.
How the BM1366 actually works
The BM1366 represents a real architectural shift from the older S17/S19-class ASIC chips like the BM1398. Instead of the host computing midstates and streaming them to the chip, the BM1366 receives an 82-byte full block header over its UART and computes the SHA-256 midstate internally. This simplifies the work-dispatch path and is part of why the chip pairs so cleanly with a low-cost ESP32 controller in the Bitaxe rather than needing a full FPGA.
It also performs hardware version rolling for AsicBoost on-chip. A version-rolling register enables the chip to iterate the block-header version bits (the BIP320 mask covering the configurable range) entirely in silicon, expanding the search space without the pool or host having to enumerate those headers. A practical consequence for firmware authors: the chip rolls those bits whether or not a pool negotiated version rolling, so the share-submission path must reconstruct the rolled version it actually hashed — otherwise the vast majority of valid work gets silently discarded. This is one of the load-bearing lessons the open-source firmware community has had to relearn the hard way.
Voltage delivery differs by host. On industrial S19 XP / S19k Pro boards the chips sit in series-stacked domains fed from the board rail, while the Bitaxe drives a single chip from a TPS546 buck regulator at roughly 1.2 V. Because every chip in a domain shares current, a single weak BM1366 can drag down its whole domain — a recurring theme in ASIC troubleshooting when a board posts a partial hashrate or fails a chip count.
Why the BM1366 matters for miners
For an operator, the BM1366 is the dividing line between "legacy 5 nm efficient" and the current 3 nm generation. It is meaningfully more efficient than the 7 nm BM139x chips that came before it, yet it is widely available on the secondary market as S19 XP and S19k Pro units age out of large hashcenters. That combination — proven silicon, large installed base, repairable boards — makes BM1366 hardware a sweet spot for home miners and small operations who want strong efficiency (J/TH) without paying flagship prices.
It is also the most approachable on-ramp to running your own node-and-miner stack. A single BM1366 on a Bitaxe lets you solo mine, learn the Stratum and chip-init internals, and keep one more layer of the network decentralized — all from a device that fits on a desk. The same chip knowledge transfers directly up to a full S19 XP, so what you learn on a single-chip Bitaxe applies at 140 TH/s.
If you are sourcing BM1366 hardware — whether a fully built S19 XP for a heated workshop or a single-chip board to learn on — D-Central stocks both industrial Antminers and open-source kits. Browse the miners catalog or the open-source mining gear to find a BM1366 platform that fits your power budget and your sovereignty goals.