Bitaxe Ultra

You want to run a small, open-source Bitcoin miner on your own node, and someone has offered you a Bitaxe Ultra cheap. Before you say yes, know what it is: the older single-chip board the Gamma has largely replaced. It is a proper little miner, the same idea as everything else in the Bitaxe line, one Bitmain ASIC on an open board hunting for a block it will almost certainly never find. The catch is timing. The Ultra came first, and the newer Gamma does more than twice the work for about the same outlay.

The take

If you are buying new at anything near list price, buy the Gamma instead. That is the honest headline and it is worth getting out of the way early. The Ultra runs a single BM1366 chip, the silicon from Bitmain’s Antminer S19 XP, and it does its job well enough. But it lands around 425 to 500 GH/s where the Gamma’s BM1370 does roughly 1.2 TH/s, and it does so at worse efficiency, for money that is now close to identical. The project and the community have moved on. Vendors carry the Ultra as leftover stock, often out of stock, rather than as a current product.

Where the Ultra still makes sense is the secondhand shelf. If one turns up for pennies, and you already run AxeOS and fancy a second low-power node pointed at your own Bitcoin Core, then it is a fine little thing to own. You are buying it for the tinkering and the extra lottery ticket, not the throughput. Bought with that expectation, nobody comes away disappointed.

What the numbers actually mean

The efficiency sits in the mid-20s J/TH, which is genuinely good hardware, right in industrial-ASIC territory. The problem is the same one every Bitaxe has, only more so here: that efficiency is spread over almost no hashrate. Half a terahash against the global network is a rounding error, so your daily output is tiny and a solo block find is a pure lottery win. Power draw around 11 to 15W means you can leave it on permanently for the cost of a nightlight, which is the real appeal of the whole class.

The comparison that matters is not the Ultra against a farm, it is the Ultra against the Gamma. Same shape, same firmware, same solo-mining story, but the Gamma does the work of roughly two and a half Ultras from one board at better efficiency. That is why the recommendation is what it is.

Overclocking, and where it stops

Mine, if I had one, ships at 485 MHz and about 1150 mV, which is where I would leave it for quiet and forget. The appeal of an open board is that you can push it, and owners do. The method is the boring one that works: raise the frequency a step, leave it an hour, watch the hardware error rate on the AxeOS dashboard, and if errors climb past a percent or two, add core voltage in 25 mV nudges rather than dropping the clock back. Around 525 to 600 MHz and up to 1250 mV, boards settle at roughly 600 to 700 GH/s, which is about as far as the stock cooler and the onboard power delivery want to go on air.

Two things run out before the paper headroom does. The BM1366 starts shedding hashes once it climbs past about 65 to 70C, so cooling is the first wall. And the power delivery on the board has a narrow window, so pushing voltage hard is as likely to trip a fault as to buy you hashrate. You will see figures past 700 GH/s posted with heavy aftermarket or immersion cooling. Fun to watch, not a daily driver.

The bit that actually breaks: power

If an Ultra goes flaky, look at the plug before you touch the clocks. The board’s TPS546 regulator wants a steady input around 4.8V, and a lot of cheap 5V supplies simply cannot hold voltage under sustained load. The input sags, the board throws a power fault or the ESP32 quietly reboots on its watchdog, and it looks for all the world like a dying board when it is really a tired charger. A decent supply fixes most of it. The 5.5 by 2.1mm barrel jack can also work itself loose over time, so if a stable unit suddenly drops out, wiggle the plug before you panic. And chip quality is a lottery, so one unit runs clean at its rated speed while the next wants more voltage to do the same job. That is binned silicon, not a fault.

On noise, the honest version is that the Ultra is quiet in volume but not in character. The stock 40mm fan has a thin, high-pitched whine that a lot of owners find more irritating than a louder but smoother fan would be. The standard fix, and it is close to universal in the community, is to swap the stock fan for a 5V Noctua NF-A4x10, which brings it down to near silent for a small loss of static pressure. If the thing is going to live on your desk, do that mod on day one.

About the RGB and the remote

If your Ultra came with an infrared remote and a hundred lighting effects, that is not a stock Bitaxe. A plain Ultra 204 has a small OLED screen and no RGB at all. The lights and the remote come from TinyChipHub’s RGBitaxe build, which takes the same Ultra board and wraps it in a custom case with LED rings and a controller. There is nothing wrong with that, it looks the part on a shelf, but it is a vendor add-on rather than anything the Bitaxe project ships, and it is worth knowing what you are actually paying for.

Who should get one, and who shouldn’t

Get one if it is cheap and used, if you already run AxeOS and want a second quiet node for your own pool, or if you specifically want the older board to tinker with. On those terms it is a likeable little miner.

Don’t get one new at full price. The Bitaxe Gamma 601 is the successor, does more than twice the hashrate at better efficiency for similar money, and is the board the whole community now points new buyers at. Skip the Ultra too if you are doing payback sums, because you will not get there on either board, and skip it if you want current stock and active support rather than legacy hardware. For most people, the Ultra is a used-only proposition now, and that is the honest place to leave it.