Definition
The BM1370 is one of Bitmain’s fifth-generation SHA-256 mining ASICs, the silicon that powers the high-efficiency variants of the Antminer S21 family. It is the die that drives the S21 Pro, and it is also the chip at the heart of the single-chip BitAxe Gamma. It belongs to the same modern “full-header” ASIC family as the BM1366 and BM1368.
Where the BM1370 fits in the Antminer line-up
A common point of confusion is which Antminer carries which die. The base Antminer S21 is built on the BM1368. The BM1370 is the Pro-tier chip: it appears in the S21 Pro (and the single-chip Bitaxe Gamma). The base S21 and the S21+ use the BM1368, while the S21 XP uses a different fifth-generation die. The BM1370 and BM1368 are close cousins on the same process generation (TSMC 5 nm) and share much of the same internal architecture, but Bitmain reserves the BM1370 for its higher-hashrate, higher-efficiency SKUs. The chip reports a hardware identifier of 0x1370 when an init routine queries the chain, which is how mining firmware tells it apart from the 0x1368 of a stock S21.
Each BM1370 die packs roughly 1,280 hashing cores. When dozens of these chips are wired in series across a hashboard, the result is the high terahash-per-second figures the S21 Pro is known for, at the leading edge of joules-per-terahash (J/TH) efficiency for air-cooled gear at the time of its release.
How it actually computes hashes
The BM1370 runs the SHA-256 double-hash that secures Bitcoin. Unlike older S9-era silicon, where the host control board computed an intermediate “midstate” and fed it to the chip, the BM1370 family receives the full 80-byte block header on the wire and computes the midstate internally. This simplifies the firmware’s job and reduces the data sent across the serial link to the hashboard.
The chip also performs on-chip version rolling (the AsicBoost / BIP320 technique). It mutates the version field of the header itself to expand the search space, rather than relying on the pool to hand it pre-rolled work. This is an important detail for anyone writing or reverse-engineering firmware: because the chip rolls the version field whether or not the pool negotiated it, the firmware’s share-submission path has to reconstruct the exact version bits the chip used before reporting a found share. Get this wrong and the overwhelming majority of otherwise-valid work is silently discarded — the hashboard looks busy while the pool sees almost nothing.
Power, voltage, and the control board
On the industrial S21 Pro and its siblings, the BM1370 is grouped into voltage domains down the hashboard, with chips in a domain sharing a regulated supply rail rather than each chip having its own independent voltage. Voltage on these boards is handled through the control board’s regulation hardware (the S21 NoPic family uses audio-class DACs on the I²C bus rather than the discrete PIC microcontrollers found on older S9-generation boards). Practically, this means tuning happens at the domain and board level — frequency and voltage are calculated at runtime to hit a target efficiency, not read from a fixed table of presets.
For miners, the takeaway is straightforward: more hashrate per watt directly improves the economics of a deployment, whether you are paying retail power rates in a home setup or wholesale rates in a Hashcenter. The BM1370’s efficiency is the main reason the S21 Pro became a reference point for new builds.
The BM1370 and open-source mining
The same BM1370 die used in industrial Antminers also lands in small open-source devices. The BitAxe Gamma is a single-chip board built around it, putting a current-generation Bitmain ASIC in the hands of solo miners and tinkerers without a full S21. This is part of why the line between “industrial silicon” and “hobbyist hardware” keeps blurring: the chip is the same, only the surrounding control board, power delivery, and firmware differ. As newer dies migrate into open-hardware designs, home miners inherit the efficiency gains that were once exclusive to data-floor machines.
This open-source direction is exactly where D-Central’s work is focused — building firmware and tooling that treats sovereign, self-hosted mining as a first-class use case. If you want to put a current-generation chip to work on your own terms, the BitAxe hub is a good place to start, and the open-source hardware catalog covers the boards that carry chips like the BM1370.
Related terms: BM1368, BM1366, ASIC Chip, SHA-256, Efficiency (J/TH), Hashboard.
In Simple Terms
Bitmain's latest mining chip in the Antminer S21. Industry-leading efficiency at approximately 15 J/TH.
The BM1370 is one of Bitmain's fifth-generation SHA-256 mining ASICs, the silicon that powers the high-efficiency variants of the Antminer S21 family. It is the die that drives the S21 Pro, and it is also the chip at the heart of the single-chip BitAxe Gamma. It belongs to the same modern "full-header" ASIC family as the BM1366 and BM1368.
Where the BM1370 fits in the Antminer line-up
A common point of confusion is which Antminer carries which die. The base Antminer S21 is built on the BM1368. The BM1370 is the Pro-tier chip: it appears in the S21 Pro (and the single-chip Bitaxe Gamma). The base S21 and the S21+ use the BM1368, while the S21 XP uses a different fifth-generation die. The BM1370 and BM1368 are close cousins on the same process generation (TSMC 5 nm) and share much of the same internal architecture, but Bitmain reserves the BM1370 for its higher-hashrate, higher-efficiency SKUs. The chip reports a hardware identifier of 0x1370 when an init routine queries the chain, which is how mining firmware tells it apart from the 0x1368 of a stock S21.
Each BM1370 die packs roughly 1,280 hashing cores. When dozens of these chips are wired in series across a hashboard, the result is the high terahash-per-second figures the S21 Pro is known for, at the leading edge of joules-per-terahash (J/TH) efficiency for air-cooled gear at the time of its release.
How it actually computes hashes
The BM1370 runs the SHA-256 double-hash that secures Bitcoin. Unlike older S9-era silicon, where the host control board computed an intermediate "midstate" and fed it to the chip, the BM1370 family receives the full 80-byte block header on the wire and computes the midstate internally. This simplifies the firmware's job and reduces the data sent across the serial link to the hashboard.
The chip also performs on-chip version rolling (the AsicBoost / BIP320 technique). It mutates the version field of the header itself to expand the search space, rather than relying on the pool to hand it pre-rolled work. This is an important detail for anyone writing or reverse-engineering firmware: because the chip rolls the version field whether or not the pool negotiated it, the firmware's share-submission path has to reconstruct the exact version bits the chip used before reporting a found share. Get this wrong and the overwhelming majority of otherwise-valid work is silently discarded — the hashboard looks busy while the pool sees almost nothing.
Power, voltage, and the control board
On the industrial S21 Pro and its siblings, the BM1370 is grouped into voltage domains down the hashboard, with chips in a domain sharing a regulated supply rail rather than each chip having its own independent voltage. Voltage on these boards is handled through the control board's regulation hardware (the S21 NoPic family uses audio-class DACs on the I²C bus rather than the discrete PIC microcontrollers found on older S9-generation boards). Practically, this means tuning happens at the domain and board level — frequency and voltage are calculated at runtime to hit a target efficiency, not read from a fixed table of presets.
For miners, the takeaway is straightforward: more hashrate per watt directly improves the economics of a deployment, whether you are paying retail power rates in a home setup or wholesale rates in a Hashcenter. The BM1370's efficiency is the main reason the S21 Pro became a reference point for new builds.
The BM1370 and open-source mining
The same BM1370 die used in industrial Antminers also lands in small open-source devices. The BitAxe Gamma is a single-chip board built around it, putting a current-generation Bitmain ASIC in the hands of solo miners and tinkerers without a full S21. This is part of why the line between "industrial silicon" and "hobbyist hardware" keeps blurring: the chip is the same, only the surrounding control board, power delivery, and firmware differ. As newer dies migrate into open-hardware designs, home miners inherit the efficiency gains that were once exclusive to data-floor machines.
This open-source direction is exactly where D-Central's work is focused — building firmware and tooling that treats sovereign, self-hosted mining as a first-class use case. If you want to put a current-generation chip to work on your own terms, the BitAxe hub is a good place to start, and the open-source hardware catalog covers the boards that carry chips like the BM1370.
Related terms: BM1368, BM1366, ASIC Chip, SHA-256, Efficiency (J/TH), Hashboard.