Bitmain Antminer K7 (63.5Th)

The Bitmain Antminer K7 (63.5 Th) is a single-algorithm ASIC built to mine Nervos CKB on the Eaglesong proof-of-work. It pairs three hashboards with an APW12-class power supply for a rated 63.5 TH/s at roughly 3,080 W — about 48.5 J/TH on Eaglesong. It is a 240 V altcoin machine, not a Bitcoin miner.

What the Antminer K7 actually is

Bitmain built the K7 for one job: hashing the Eaglesong function that secures the Nervos Common Knowledge Base (CKB) network. Eaglesong is a purpose-designed ARX hash, and the K7’s silicon does nothing else — it cannot mine Bitcoin (SHA-256), Litecoin (Scrypt), or any other coin. That single-purpose design is the most important fact to understand before buying one: its resale value, profitability, and useful life are tied entirely to the health of the Nervos CKB network and its Eaglesong difficulty.

The 63.5 Th unit is the higher-binned member of the K7 family; Bitmain also shipped a slightly lower-clocked 58 Th sibling on the same chassis. Both descend from the earlier Antminer K5, Bitmain’s first-generation Eaglesong machine, and the K7 represents a large generational jump in throughput per box.

Chip and hashboard architecture

The K7 follows the same modular template as every modern air-cooled Antminer: a single Linux control board running a cgminer-derived mining daemon, three hashboard chains (Chain 0/1/2), an APW-series PSU, and a bank of fans, all wired together inside the familiar 430 × 195.5 × 290 mm sheet-metal case. The control board talks to each hashboard over an 18-pin ribbon cable that carries low-voltage power, ground, and the digital signal chain (clock, serial TX/RX, reset, and an I²C temperature-sensor bus).

On each board, Bitmain’s custom Eaglesong ASICs are daisy-chained in series and fed by a boost circuit that steps the PSU rail up into a string of voltage domains. This is a detail many spec sheets get wrong: voltage on an Antminer hashboard is regulated per domain, not per chip. A « domain » is a small group of chips sharing one regulated rail in series, so the firmware can only trim voltage at the domain level — never one chip at a time. Understanding that distinction is the difference between a productive board-level repair and chasing a fault that the hardware was never designed to expose.

D-Central does not publish an invented per-chip count for the K7’s Eaglesong silicon, because the manufacturer never documented the exact die population per board and we will not guess at numbers we cannot verify. What we can say with confidence is structural: it is a three-chain, series-domain Antminer, and it behaves on the bench like its APW12-family stablemates.

Real-world power and efficiency

The published 3,080 W figure is a wall-side rating at room temperature with a roughly ±5% tolerance, so in practice a healthy K7 pulls somewhere in the region of 2,930–3,230 W depending on ambient temperature, PSU conversion loss, and how hard the pool is pushing it. The conversion losses of the power supply are already baked into that wall figure — the PSU itself runs at roughly 93–95% efficiency.

Efficiency works out to about 48.5 J/TH on Eaglesong. That number must be read in context: a joule-per-terahash figure is only comparable within the same algorithm. You cannot line the K7’s 48.5 J/TH up against a modern SHA-256 Bitcoin miner at 15–20 J/TH and conclude it is « inefficient » — Eaglesong and SHA-256 are different functions doing different amounts of work per hash. Judge the K7 only against other CKB miners.

A critical practical point for North American buyers: the K7’s APW12 (1417-series) supply is a 200–240 V unit. It is not a 120 V machine, and it cannot be made into one — a standard household 15 A/120 V circuit will not run it. You need a 240 V drop, the same as you would for an Antminer L7 or S19. Tuning headroom on the K7 is modest compared with the deep undervolting possible on the Bitcoin fleet, but there is room to trade a little hashrate for efficiency or vice-versa. For how that trade-off works in general — and the tooling we use to find a stable operating point — see our ASIC power profiles reference.

Firmware compatibility — the honest picture

This is where Eaglesong owners need a reality check that most listings won’t give them. The rich aftermarket-firmware ecosystem you may have read about — the third-party operating systems that add autotuning, finer voltage steps, and advanced pool features — was built almost exclusively for SHA-256 Bitcoin hardware (the S19 and S21 families and their kin). Those projects do not target Eaglesong machines, and there is no mature third-party firmware for the K7. Our own DCENT_OS work is likewise Bitcoin-focused and does not cover this model.

In plain terms: you run the K7 on Bitmain’s stock firmware, and your tuning is whatever the stock interface exposes. That is not a knock on the machine — it is simply the state of the altcoin-ASIC software world, and we would rather tell you up front than have you buy expecting an autotuner that doesn’t exist. Keep the stock firmware patched, change the default credentials, and isolate the miner on its own network segment.

Common faults and troubleshooting

Because the K7 shares the Antminer control architecture, it also shares the same failure vocabulary as the rest of the fleet. The faults we see most often on three-chain machines like this are:

• A chain dropping out — the dashboard shows two boards instead of three, or reports « 0 ASIC » found on a chain. Usually a dead domain, a failed chip breaking the series string, or a damaged signal cable.
• Low chip/ASIC count or reduced hashrate — one or more chips in a chain have failed, so the board reports fewer working ASICs and the box falls short of 63.5 TH/s.
• Temperature-sensor errors — a board reports an implausible or missing temperature, tripping a protective shutdown; often the I²C sensor line rather than an actual overheat.
• Fan errors — a stalled or out-of-range fan, which the firmware treats as a hard fault and refuses to mine through.
• PSU communication / power faults — the APW12 supply is a smart unit that talks to the control board over I²C; a comms fault can look like a « no power » or under-voltage condition.

If your K7 is throwing one of these, our ASIC fault finder walks symptom-to-cause and points to the right next step before you start swapping parts.

Repair and longevity

The K7 is a repairable machine, and D-Central has repaired Antminers in-house in Laval since 2016. It sits firmly within the set of models supported by the hashboard test fixtures and PSU testers we and the wider repair trade use, so chain-level diagnosis, dead-chip identification, and board-level rework are all on the table rather than a forced full-unit write-off. Typical economically-sensible repairs include reflowing or replacing failed Eaglesong chips on a single chain, restoring a dead voltage domain, recovering a board after a cable or connector fault, and servicing the APW12 supply.

Because the PSU is shared with the Antminer L7, KA3, DR7 and HS3, parts knowledge and spares are comparatively easy to source — a meaningful advantage for keeping an aging altcoin rig productive. If your unit is down, our ASIC repair service can assess it and quote a board-level fix.

Who the K7 is for — and buying notes

The K7 is for miners who specifically want exposure to Nervos CKB and have the infrastructure to run a ~3 kW, 240 V, fan-cooled industrial box: a dedicated circuit, real airflow, and tolerance for jet-engine noise. It is not a home-friendly or Bitcoin machine, and Bitcoiners looking to stack sats or learn solo mining are far better served by a SHA-256 unit or a small Bitaxe-class device than by an Eaglesong miner. Treat any CKB profitability estimate as volatile — single-algorithm altcoin ASICs live and die by one network’s price and difficulty.

If the K7 fits your plan, decide between the 63.5 Th unit here and its lower-power 58 Th sibling, and browse the full ASIC miner catalog to compare it against current and used inventory.

Generational context

The K7 sits in Bitmain’s altcoin lineup rather than its Bitcoin line. It directly succeeds the Antminer K5, Bitmain’s first Eaglesong/CKB miner, multiplying throughput per chassis many times over. Alongside it, Bitmain shipped a family of single-algorithm machines that share the same 14–17 V APW12 power platform — the Scrypt L7, the Kadena KA3, the Decred DR7, and the Handshake HS3 — which is why these units feel so similar on the bench despite mining completely different coins. Launched in late 2023, the K7 remains the reference Eaglesong ASIC for anyone committed to securing the Nervos network, and a machine D-Central is equipped to keep running long after its warranty ends.