Bitaxe Supra

The Bitaxe Supra is an open-source, single-chip desktop Bitcoin miner built around one Bitmain BM1368 ASIC — the same TSMC 5 nm silicon used in the industrial Antminer S21. It delivers roughly 700 GH/s at about 12 W (≈17 J/TH), runs near-silent, and is built for solo “lottery” mining, learning the hardware, and supplemental heat.

Chip and board architecture

At the heart of the Supra is a single Bitmain BM1368, a TSMC 5 nm SHA-256 ASIC from Bitmain’s 2023 (Gen 5) generation — the identical part that fills the hashboards of the Antminer S21. The chip carries 1,280 hashing cores, organised as 80 “big” cores each containing 16 “small” cores, and reports the identity register 0x1368 over its serial interface. It belongs to the “no-PIC” generation: unlike older S9-era boards, there is no separate PIC microcontroller heartbeat to authorise the hashboard, which is one reason the BM1368 was straightforward to bring up on open hardware.

Where an industrial S21 daisy-chains 108 of these chips per hashboard, the Supra runs exactly one. That single ASIC is driven by an ESP32-S3 control board — a dual-core 240 MHz microcontroller with integrated WiFi — that handles pool networking, the web interface, and the OLED stats display, and talks to the ASIC over a single UART (TX on GPIO 17, RX on GPIO 18) starting at 115,200 baud and stepping up to 1 Mbaud once the chip is initialised. A small SSD1306 OLED shows live hashrate and temperature, and an EMC2101 combines the board temperature sensor and single-fan PWM control.

Power delivery is worth understanding, because it is a common source of confusion. On a full S21 hashboard the chips are wired in series and grouped into voltage domains, and voltage is regulated per domain — not per individual chip. The Supra collapses that scheme to its simplest form: a single chip is a single domain, fed by one onboard TPS546 step-down (buck) regulator that converts the 5 V input down to roughly 1.2 V of core voltage at high current. Power comes in through a 5 V DC barrel jack (5.5 × 2.1 mm) — not USB-C, so a quality 5 V adapter with generous headroom is essential.

Real-world power and efficiency

In its stock tune the BM1368 in a Supra runs near ~490 MHz at about 1.20 V, producing roughly 700 GH/s while drawing about 12 W at the wall. That wall figure is the whole board — the ASIC plus the fixed overhead of the ESP32-S3, the regulator, the fan, and the display (on the order of a couple of watts). Dividing it out gives an efficiency near 17 J/TH.

That number is honestly higher (worse) than a fully populated S21, which lands closer to ~17.5 J/TH per hashboard. This is not a weakness of the silicon — it is the same chip — but the arithmetic of desktop scale: one chip has to carry the entire board’s fixed overhead, whereas a 108-chip machine amortises its controller, fans, and PSU across far more terahashes. You are paying a small efficiency premium for a self-contained, near-silent device you can keep on a desk.

There is real tuning headroom in both directions. The AxeOS firmware exposes core frequency and core voltage directly: push the frequency higher for more GH/s at a worse J/TH and more heat, or undervolt and underclock for better efficiency, lower noise, and longer chip life. The on-board firmware computes the PLL divider settings for your target frequency at runtime — these are solved on the fly, not loaded from a fixed preset table — so the chip can be moved across a wide frequency range cleanly. For a structured look at how frequency and voltage trade against hashrate and efficiency on Bitmain silicon, see our ASIC power profiles database. As a heat source, ~12 W equates to roughly 41 BTU/h — modest, but genuinely useful as a silent, always-on supplement in a small room.

Firmware compatibility

The Supra ships with ESP-Miner / AxeOS, the open-source (GPL-3.0) firmware from the bitaxeorg project. Credit where it is due: the Bitaxe design and its firmware are the work of Skot Croshere and the open-source community that grew up around the project, and they are the reason a single S21-class chip can be owned, flashed, and audited end to end. AxeOS gives you a clean web UI to set your pool, frequency, and voltage, watch live hashrate and temperature, and apply over-the-air updates.

On the protocol side, AxeOS speaks Stratum V1. It is worth being precise here: among Bitmain-class firmwares, only BraiinsOS+ natively speaks Stratum V2, and that is an Antminer-firmware distinction — not a feature of the Bitaxe line. In practice you point a Supra at a Stratum V1 endpoint: a public solo pool, a shared pool, or — most in keeping with the device’s spirit — your own Bitcoin node running a solo stratum server such as CKpool. Community firmware forks (the NerdAxe / NerdQAxe family and others) exist if you want to experiment. D-Central also maintains its own open driver for the BM1368 and has driven the chip to first hash on bench hardware; that firmware work for this class of board is currently in closed beta.

Common faults and troubleshooting

Because the Supra runs a single ASIC, that chip is a single point of failure — if it dies the board stops hashing, whereas a 108-chip S21 can limp along on partial boards. The good news is that the failure modes are few and well understood:

For a guided, step-by-step walkthrough that covers the same diagnostic logic we use on industrial Antminers, work through our ASIC fault finder.

Repair and longevity

D-Central has been repairing Bitmain ASIC hardware in-house since 2016, and the BM1368 on your Supra is the exact silicon we service at scale on S21 hashboards. Board-level service is realistic here: the barrel jack, the TPS546 regulator, the fan, and the ESP32-S3 are all serviceable or replaceable, and a suspect ASIC can be reflowed or diagnosed on the bench. We will be honest about the economics — at this device’s entry-level price, a full board repair can occasionally cost more than simply replacing the unit, so the most valuable thing we offer is a quick, accurate diagnosis of whether the chip or the board is at fault. If you want a chip-level opinion, or you are running a small rack of these, our ASIC repair bench can help.

For longevity, the single best lever is heat: run the Supra slightly undervolted and underclocked and it will sit cool and quiet for years. Keep the firmware current, keep the heatsink clean, and give it a power supply with margin.

Who it is for and buying

The Supra is built for the sovereign Bitcoiner, not the spreadsheet. It suits solo “lottery” miners taking a shot at a full block reward, people who want to mine against their own node, tinkerers learning the Stratum protocol and ASIC bring-up, and anyone who wants a near-silent desk companion that doubles as a trickle of heat. Be clear-eyed about returns: at ~700 GH/s against a global network measured in hundreds of exahashes, a single Supra is a lottery ticket, not an income stream — its value is sovereignty, education, and heat, not ROI.

If you want more hashrate or a different chip, compare it within the family: the Bitaxe Ultra (BM1366, the S19 XP chip), the Bitaxe Gamma (BM1370, the S21 Pro chip), and the multi-chip Hex and QAxe boards for more terahashes per box. Browse the full line-up on our Bitaxe hub or the complete ASIC miner catalog.

Generational context

The BM1368 sits squarely in the middle of Bitmain’s Gen-5 trio: it succeeds the BM1366 (S19 XP / S19k Pro, and the Bitaxe Ultra) and is joined by the BM1370 (S21 Pro and the Bitaxe Gamma). All three share the same serial protocol family and the same ESP-Miner driver lineage, which is why the Bitaxe line could grow one chip at a time. The BM1368’s notable step over the BM1366 was doubling the small cores per big core — 16 instead of 8 — and shedding the legacy PIC, both of which are visible in how the chip is addressed and initialised.

Ultimately the Supra is the open-source, single-chip distillation of the Antminer S21. Credit belongs to Bitmain for the silicon and to the bitaxeorg community for making it hackable; D-Central’s contribution is keeping that silicon alive, accurate documentation, and chip-level repair. Running one S21 chip on your own desk, pointed at your own node, on firmware you can read — that is one more layer decentralized.