BM1370: The ASIC Chip That Brought Home Mining Back
Werner BundschuhShare
If you own a Bitaxe Gamma, a NerdQaxe++, or a BitForge Nano, there's a small piece of silicon inside that was never actually meant for you: the BM1370. Bitmain developed it for their industrial Antminer S21 Pro – thousands of them are humming away in mining farms with megawatt power connections. The fact that the same chip is now sitting quietly on your desk is the direct result of years of reverse-engineering work by the open-source mining community.
This article explains what the BM1370 can really do, where it comes from, and why it's the most important mining chip of its generation – no marketing speak, no fabricated numbers.
The BM1370 is Bitmain's current SHA-256 mining ASIC, manufactured on TSMC's 5 nm process. A single chip delivers 1.0–1.2 TH/s at around 18 W (15 J/TH efficiency) at stock settings. In industrial hardware like the Antminer S21 Pro, 252 of them work in parallel to produce 234 TH/s at 3,531 W. In the open-source world, the same chip powers compact home miners: one per Bitaxe Gamma, two per Bitaxe GT and BitForge Nano, four per NerdQaxe++. With good cooling, it can be overclocked to over 2 TH/s per chip – the largest overclocking headroom of any chip ever used in open-source Bitaxe designs.
The Story: How an Industrial Chip Ended Up on Your Desk
To understand the BM1370, you have to know the story of the Bitaxe project. Skot9000 – real name Skot Croshere – is an electrical engineer and Bitcoiner. In early 2023, he asked himself: What if you could pull the ASIC chips out of Bitmain's industrial miners and put them on a simple, open board that anyone could run at home?
The problem: Bitmain publishes no datasheets for its ASICs. There are no register maps, no communication protocols, no official specifications. Anyone wanting to drive a BM1397, BM1366, BM1368, or BM1370 has to start from scratch.
That's exactly what Skot did. Over the course of years, he physically disassembled Bitmain hardware, used oscilloscopes to capture the communication between controller and ASIC, measured voltages, and step by step reconstructed how each new chip works. The knowledge gained from this work lives today in the ESP-Miner firmware (better known as AxeOS) – the open-source driver for the entire Bitaxe family.
The Bitaxe generations directly trace Bitmain's chip history:
- Bitaxe Max (2023) – BM1397 from the Antminer S17, ~400 GH/s
- Bitaxe Ultra (2023) – BM1366 from the S19 XP, ~500 GH/s
- Bitaxe Supra (2024) – BM1368 from the S21, ~625–775 GH/s
- Bitaxe Gamma (August 2024) – BM1370 from the S21 Pro, 1.0–1.2 TH/s
On August 19, 2024, Skot posted on X: "The bitaxeGamma is go! The newest member in the #bitaxe lineup features the BM1370 ASIC from the Antminer S21 Pro. So far we've been able to pull 1 – 1.2 TH/s at around 15 J/TH from a single chip 🤯". That's when the era of sub-20-watt home miners with terahash-class performance began – something that had been unthinkable just months earlier.
What the BM1370 Actually Is
The BM1370 is an Application-Specific Integrated Circuit (ASIC) – a chip that can do exactly one thing: compute SHA-256 hashes. That's what Bitcoin mining is, at the hardware level. Take a block header, compute a 256-bit number from it, and hope you find one below the current difficulty target.
Unlike a processor in your computer, a BM1370 can't process text or render webpages. What it can do, it does massively in parallel: SHA-256 calculations, with an efficiency that outpaces any GPU by a factor of 60+.
Confirmed Specifications
| Parameter | Value |
|---|---|
| Hashrate (stock) | 1.0–1.2 TH/s per chip |
| Efficiency (stock) | ~15 J/TH |
| Power consumption (stock) | ~15–18 W per chip |
| Manufacturing process | 5 nm class (TSMC, not officially confirmed) |
| Algorithm | SHA-256 (double-hash) |
| Voltage (typical) | 1.15–1.25 V core voltage |
| Frequency (stock) | ~525 MHz |
| Frequency (overclock ceiling) | 900–1,000 MHz (with adequate cooling) |
| Package | BGA with 300+ solder balls (micro-BGA) |
Important note on the manufacturing process: Bitmain never officially confirms the exact node. The industry consensus on the BM1370 family is 5 nm. Earlier Bitaxe generations with BM1366/BM1368 use the same or a very similar 5 nm process; what sets the BM1370 apart is architectural design improvements, not a shrink to a smaller node.
The Chip Family: Not Every BM1370 Is Equal
Something many people don't realize: "BM1370" is actually an entire family of chip variants. Zeus Mining and other repair specialists list at least six variants: BM1370AA, BM1370BB, BM1370BC, BM1370PA, BM1370PB, and BM1370PF. They all come from the same wafer production at TSMC, but they go through a process called speed binning.
What does that mean? Even within the same wafer lot, individual dies behave slightly differently. Some run stable at lower voltages, others need more; some manage 1,000 MHz, others top out at 750 MHz. Bitmain tests every chip after manufacturing and sorts them into performance tiers:
- Top-bin chips with the best efficiency go into premium products like the S21 Pro
- Middle bins end up in standard S21 models
- Lower bins go to the repair market – and through third parties, occasionally into open-source boards
This variation is known in the community as the "silicon lottery": two visually identical Bitaxe Gamma units can behave significantly differently when overclocked. One might stably reach 1.8 TH/s, the other becomes unstable at 1.5 TH/s. That's exactly why experienced miners always share their overclocking settings with the disclaimer "your mileage may vary."
Where the BM1370 Works
In Industry
Bitmain's Antminer S21 Pro was the first device to use the BM1370 – and remains by far the most important by volume. One unit packs 252 chips onto three hashboards, producing 234 TH/s at 3,531 W – exactly 15.1 J/TH. When it launched in 2024, the S21 Pro was the most efficient industrial Bitcoin miner on the market.
Successor models like the S21 XP, S21+, and S21 XP Hydro use variants of the same BM1370 – some with hydro cooling for higher clock speeds and correspondingly higher hashrate per unit.
In Open-Source Hardware
This is where it gets interesting, because all the designs are publicly available:
- Bitaxe Gamma – one BM1370, 1.0–1.2 TH/s, ~17–18 W. The direct successor to the Bitaxe Supra line, designed by Skot personally.
- Bitaxe GT (801) – two BM1370 chips on a 6-layer PCB, ~2.4–2.6 TH/s, ~43 W. Skot's own dual-chip design.
- BitForge Nano – also dual BM1370, 2.4–2.6 TH/s, ~36 W at factory setting. Custom enclosure and ForgeOS firmware, developed in Germany.
- NerdQaxe++ – four BM1370 chips, 4.8 TH/s at ~72 W. Our current flagship: S21-Pro-level efficiency in a desktop format, Made in Germany.
- NerdOctaxe Gamma – eight BM1370 chips, ~8 TH/s at ~160 W. Currently the largest fully open single-board design.
- Bitaxe Gamma Hex – six BM1370 chips, 6+ TH/s
All of these devices share the same chip, the same open-source driver stack, and the same reverse-engineering origin. What differs is the number of chips, the PCB design, power delivery, and cooling solution.
Overclocking: The Real Potential
One of the BM1370's most remarkable properties is its overclocking headroom. While older BM1366 and BM1368 chips hit thermal limits at 550–600 MHz, many BM1370 units can stably run at 900–1,000 MHz – but only with significantly upgraded cooling.
Real-world community results:
- Stock (525 MHz / 1150 mV): 1.07 TH/s at ~12 W
- Moderate overclock (700 MHz / 1200 mV): ~1.4 TH/s at ~15 W
- Aggressive overclock (900 MHz / 1250 mV): ~1.84 TH/s at ~25 W
- Extreme (with premium cooling): over 2 TH/s from a single chip
Power draw scales nonlinearly with overclocking – efficiency degrades from ~15 J/TH to ~13–14 J/TH. In exchange, the probability of finding a block scales linearly with hashrate. For lottery miners, moderate overclocking often delivers the best electricity-cost-to-block-chance ratio.
Important: Overclocking requires better cooling. The included stock heatsink typically only supports up to ~700 MHz. For higher frequencies, premium heatsinks (pin-fin designs, larger fans) or active hydro cooling on multi-chip boards make sense.
Block Finds with BM1370 Hardware
Theory is one thing; reality is another. Here are the documented Bitcoin blocks found by open-source BM1370 hardware since the chip's release:
- March 2025 – Block #889,975: A stock Bitaxe Gamma at 1.2 TH/s finds a block. Payout: 3.149 BTC.
- September 5, 2025 – Block #913,272: First documented block find with a NerdQaxe++ (4.8 TH/s) via Ocean's pool with DATUM.
- October 27, 2025 – Block #920,440: A home setup with six NerdQaxe++ units finds a block – payout equivalent to ~$342,000.
Statistically these are outliers – the daily probability for even a NerdQaxe++ cluster is in the millions-to-one range. But that's exactly what Bitcoin is: the protocol doesn't differentiate between 234 TH/s and 1.2 TH/s. A valid hash is a valid hash.
What the BM1370 Is Not
A few myths circulate on the internet that need correcting:
"The BM1370 is manufactured on a 7 nm process." Wrong. The 15 J/TH efficiency is physically unreachable on 7 nm – the BM1366 on 5 nm was already at ~17 J/TH. Bitmain doesn't officially confirm anything, but the industry consensus is clear: BM1370 is 5 nm class.
"Mining ASICs validate transactions." Wrong. Transactions are validated by Bitcoin nodes (e.g., Bitcoin Core). The BM1370 only computes SHA-256 hashes against a prepared block header. Anyone wanting to mine truly trustlessly also needs their own full node.
"Open source means the chip is open." Wrong. The BM1370 itself is proprietary Bitmain hardware. What's open source is everything Skot and the community built around it: the PCB designs, the ESP-Miner/AxeOS firmware, the drivers, the schematics. The chip itself remains a black box – but through reverse engineering, its behavior is largely documented.
"With a Bitaxe Gamma you'll find a block every few weeks." Very, very wrong. The mathematical probability per block is roughly 1 in 670 million. Anyone buying with that expectation is in the wrong hobby. Anyone buying out of conviction – decentralization, learning, sovereignty, hobby – is in exactly the right place.
Comparison to Predecessors
| Chip | Source | Hashrate (per chip) | Efficiency | Bitaxe Model |
|---|---|---|---|---|
| BM1397 | Antminer S17 | ~400 GH/s | ~40 J/TH | Bitaxe Max |
| BM1366 | Antminer S19 XP | ~500 GH/s | ~20–25 J/TH | Bitaxe Ultra / Hex |
| BM1368 | Antminer S21 | 625–775 GH/s | ~17 J/TH | Bitaxe Supra |
| BM1370 | Antminer S21 Pro | 1.0–1.2 TH/s | ~15 J/TH | Bitaxe Gamma / GT, BitForge Nano, NerdQaxe++ |
From the BM1397 to the BM1370, hashrate per chip has roughly tripled, and efficiency has improved by a factor of about 2.5. Three years of mining hardware development, made visible through open-source reverse engineering.
FAQ
Can I buy individual BM1370 chips?
Yes, but with caveats. Suppliers like TinyChipHub (an official Bitaxe manufacturer), Zeus Mining, or Bitmars sell individual chips starting at about $15–25 each. Zeus Mining and Bitmars primarily sell repair chips for defective S21 Pro hashboards. Important: Installation requires a BGA rework station, a reflow oven with precise temperature control, and ESD protection – this is not a DIY hot-air-gun job. Even experienced technicians report failure rates above 40% on BGA swaps.
Why is the BM1370 in open-source boards so good despite the "top-bin theory"?
Because "worse than top-bin in the S21 Pro" is still excellent. The efficiency difference between a top-bin and a mid-bin chip is typically 5–10%. For home mining with a lottery character, that's irrelevant – electricity costs are single-digit dollars per month anyway.
How many BM1370 chips have been produced?
Bitmain doesn't publish exact numbers, but the order of magnitude can be estimated: with 252 chips per S21 Pro and several hundred thousand units produced for industry alone, the total is likely over 100 million chips. Of these, a tiny single-digit percentage ends up in the open-source market.
What's the successor to the BM1370?
Bitmain has announced successor chips – industry rumors point to a BM1372 or BM1380 on a 3 nm process, targeting efficiency under 12 J/TH. Competitors like Auradine (AT2880) and Block (Proto, Jack Dorsey's mining project) are also developing 3 nm chips. Open-source Bitaxe hardware with these chips will likely arrive in late 2026 at the earliest – once Skot and the OSMU community have reverse-engineered them.
Does the ESP-Miner firmware work with all BM1370 variants?
Essentially yes. The Bitaxe community firmware supports all common BM1370 sub-variants (BB, BC, AA, PA, PB). The initialization sequence and Stratum protocol are the same for all – differences only show up in specific overclocking behavior and thermal characteristics.
Conclusion: Why the BM1370 Matters
The BM1370 isn't just a chip – it's the result of a long chain: Bitmain invests hundreds of millions of dollars in an ASIC for industrial mining farms. Skot9000 and the Open Source Miners United invest thousands of hours in reverse engineering. Manufacturers like TinyChipHub, D-Central, BitForge, and Solomining build hardware on top of it that you can put on your desk.
The result: a single person with a Bitaxe Gamma costing €200–300 today has a real, mathematically existing chance of finding a full Bitcoin block – currently worth around $280,000–340,000. That chance is vanishingly small. But it's not zero. And that's exactly what Bitcoin is at its core: a protocol that doesn't distinguish between a 234 TH/s industrial giant and a 1.2 TH/s home miner.
The BM1370 is the chip that made that possible again.
BM1370 hardware directly from us:
- 👉 Bitaxe Gamma – your entry into the BM1370 (1.2 TH/s, ~18 W)
- 👉 BitForge Nano – dual-chip design "Developed in Germany" (2.4 TH/s, ~36 W)
- 👉 NerdQaxe++ Made in Germany – our flagship with four BM1370 chips (4.8 TH/s, ~72 W)
Questions about the BM1370, overclocking, cooling, or which hardware fits your setup? Reach out – we know the chip first-hand.
Sources: Bitaxe Gamma GitHub, Skot9000 (X), Bitcoin Magazine, D-Central – ASIC Fabrication, D-Central – Bitaxe Overclocking Guide, DTV Electronics – BM1370 ASIC Chip. As of May 2026.