Fallback pool and dual pool on a Bitaxe or a NerdQAxe

A fallback pool A server that machines connect to. A regular pool shares the earnings, a solo pool does not. Solo or pool? is a second server kept in reserve. The machine mines on one pool at a time, and only moves to the second one when the first stops answering.

A dual pool setup stays connected to both pools at once and splits the hashrate Computing power: the number of attempts per second of a machine or of the whole network. The higher it is, the more tickets you play in each draw. between them, for example 70% for one and 30% for the other. It is not merged mining: nothing is counted twice. A Bitaxe Gamma (1.2 TH/s rated) does not hash A 64-character code computed from the block. Impossible to predict: you have to try. any faster because it talks to two pools.

Here is what version 2.15.4 (21 October 2026), the latest release, does according to its source code:

• The switch. AxeOS moves to the fallback pool after three failed attempts in a row on the primary: address not found, connection refused or no answer within 5 seconds, connection dropped. After a failed connection it waits 5 seconds before trying again (1 second when the address cannot be found). When the server is truly unreachable, expect anything from a few seconds to about half a minute.
• The way back. After an automatic switch, AxeOS tests the primary pool every 60 seconds: it opens a test connection and waits for the pool to send work (a plain connection test for a Stratum The language machines and pools speak. V2 pool). As soon as the primary answers, it goes back.
• Manual choice. On the dashboard, the Pool card has a Primary or Fallback menu; changing pool restarts the machine. If you pick the fallback yourself, AxeOS stays on it: it no longer tests the primary every 60 seconds, and only goes back to it if the fallback fails in turn.
• Both pools down. When both fail one after the other, AxeOS stops mining and cuts power to the chip to save electricity (since 2.14.0). It tests the pools again every 30 seconds and resumes on the first one that answers.
• The counters. Every switch resets the accepted and rejected share An attempt good enough to be counted by the pool. It proves your machine is working, even if it is not enough to find a block. counters, and the dashboard shows the “Using fallback pool” warning.

The fallback pool has existed since version 2.3.0 (16 October 2024), the dashboard menu since 2.11.0 and the list of eight pools since 2.15.0. The labels and delays above apply to 2.15: on an older version, start by updating AxeOS.

1. Open AxeOS (the machine’s IP address in the browser) and click Pool in the menu.
2. Prepare Pool 2. Under Pool Configurations it often exists already: it is the old fallback pool. Open it, or create one with Add Pool (eight at most).
3. Fill in its fields: Stratum Host, Stratum Port, Stratum Protocol (V1, unless the pool speaks Stratum V2), User and Password. If you paste a full address such as stratum+tcp://host:port, AxeOS strips the prefix and moves the port to its field by itself.
4. Pick the roles at the top of the page, under Active Pool Selection: Pool 1 as Primary Pool, Pool 2 as Fallback Pool.
5. Click Save, then Restart: AxeOS warns that changes only apply after a restart.

FindMyBlock is the solo pool I built (0% fee). Solo CKPool, the second pool I use as the example in the video, belongs to another operator: 2% fee on a found block, your Bitcoin address as the user, any password. Its stratum.ckpool.org address picks the fastest-responding server by itself (USA, Europe, Asia, Oceania) and moves to another one if yours goes down.

Three traps. In the project’s factory settings for the Gamma 601, the fallback is solo.ckpool.org with an example address: if you only change the primary pool, a block found during an outage would go to that address, not yours (AxeOS then shows a yellow warning). A fallback on the same server as the primary goes down with it: pick another operator. And FindMyBlock’s port 3336, meant for rented hashrate (fixed high difficulty How many attempts it takes on average to find a block. It adjusts itself about every two weeks. Difficulty explained), sits on the same server: it is not a fallback for 3335.

On AxeOS 2.14, the same fields sit in a Fallback Pool Configuration block, under the primary pool’s; on older versions their place varies. For a first setup: set up a Bitaxe step by step.

Machines from the NerdQAxe family run shufps’s firmware (ESP-Miner-NerdQAxePlus), a separate version of AxeOS. Since release 1.0.35 (28 November 2025), it mines on two pools in parallel, on every machine of the family, down to the small single-chip NerdAxe. The stable release checked here, 1.1.0.1 (24 September 2026), ships files for the NerdAxe, NerdQAxe+, NerdQAxe++, NerdOctaxe and NerdQX, among others. My reviews: NerdQAxe++ Hydro, NerdOctaxe and NerdQX 8T.

1. Open Settings in the menu, Stratum Settings section (the interface comes in several languages, picked on the same page).
2. Pick the mode: set Pool Mode to Dual Pool. The other mode, “Failover (Primary/Fallback)”, is the classic fallback pool.
3. Set the Pool Balance slider, from 1 to 99%: 70 gives 70% to the primary pool and 30% to the secondary one.
4. Fill in both tabs: host (without stratum+tcp:// or port, as the interface reminds you), port, username and password for each pool.
5. Save, then restart if the interface asks for it.

How the hashrate is split. The firmware hands the chip a new job every 500 milliseconds (on BM1370 Bitmain's chip from the Antminer S21 Pro, also used in the Bitaxe Gamma and most recent desk miners. chips) and picks the pool each time, so that the chosen ratio holds. Each result goes back to the pool that sent the job. According to the 1.1.0.1 source code, if one of the two pools disconnects, all the hashrate goes to the other one until it returns. Since 1.0.37 (9 May 2026), one pool can run Stratum V1 and the other V2.

With a very lopsided split (99/1 for example), the minority pool may ask for a difficulty below the chip’s minimum: shares stay valid, but its hashrate estimate becomes wrong, and the interface flags it with an orange badge, “Share for this pool too small!”. In Failover mode, the firmware moves to the secondary pool when the primary disconnects (the secondary connection is attempted every 30 seconds) and drops it as soon as the primary is back.

Official AxeOS does not mine on two pools at once. A request for it was closed in April 2025 as not planned: for skot, who started the ESP-Miner repository, it is a lot of complexity for little benefit on a small single-chip miner, and hard to write for the Bitaxe’s ESP32 processor. In pull request 1795, merged in July 2026, a project developer lists multi-pool mining with a ratio per pool among long-term ideas, with no date. Nothing of the kind is in 2.15.4.

SerpentX Dual-Pool is the project I show in the video for the Bitaxe: a community fork under the GPL-3.0 licence, created in July 2026, which states it is not affiliated with the Bitaxe or NerdQAxe projects. Version checked: 1.8, 17 October 2026, for the Bitaxe Gamma (BM1370 chip), NerdAxe and NerdAxe Gamma. On a Bitaxe, the chip works for pool A and pool B in turns, in time slices of 3 seconds by default (adjustable from 0.1 to 60 seconds), so that the chosen percentage holds over time. Each share goes back to the pool that supplied the work, and each pool can have its own fallback.

1. Check the model and write down your settings. Take the files of the latest release, for your exact machine, without renaming them.
2. Install through the AxeOS update (Update page): esp-miner.bin, then www.bin, then restart. On a machine that already runs, this is the path the project recommends: a full USB flash (factory file, or the project’s web flasher) wipes Wi-Fi and settings, and is meant for a blank board or a repair.
3. Turn on dual pool in the Pool page, Dual Mining (Simultaneous Pool B) block: Enable Dual Mining, Split Interval (ms), Pool A Share %, then pool B’s host, port, user and password (Pool Password), plus its fallback if you want one.
4. Save and restart. From then on, the interval, the percentage and the on/off switch apply live; pool B’s address and credentials need a restart. Check pool A as well: 2.15 and SerpentX do not store pool settings the same way.

What to know first. The Bitaxe build is deliberately based on ESP-Miner 2.14.2: 2.15 features are not in it, and official fixes only arrive if the author ports them. Its maintenance file keeps a list of the official fixes reviewed, ported or left out. Pool B only speaks Stratum V1. The video dates from 12 October, when the latest release was 1.6: 1.7 (16 October) fixes two dual-pool bugs, including a pool A outage that also stopped pool B. Finally, the built-in updater offers SerpentX releases: to go back to official firmware, upload the latest official file by hand, following its release notes (since 2.15.0 the interface is included in esp-miner.bin).

No. Each pool only sees its share of the hashrate, and the odds are split in the same proportions. Between two Bitcoin solo pools they add up: 1 in 22,800 plus 1 in 53,200 a year still make 1 in 16,000, just as without a split. The figures for a Bitaxe Gamma:

For your own machine, the solo mining calculator runs the same math live. For the regular pool share, keep the order of magnitude in mind: a whole Gamma would earn about €14 a year on average in a regular pool, before fees and electricity.

• Fallback pool, on AxeOS. The dashboard’s Pool card shows the active pool (Primary or Fallback) and its address. To test the switch, deliberately break the primary pool’s host, save and restart: the Logs page should show “Max V1 retry attempts reached (3)”, then “Switching to fallback pool”, and your machine should appear on the fallback pool’s site. Put the right host back, save, restart: back to the primary. In the API (/api/system/info), the isUsingFallbackStratum field reads 1 on the fallback.
• Dual pool, at the pools. Look up your address on each pool’s site: your machine should show up with a hashrate close to its share, around 0.84 TH/s at the 70% pool for a Gamma. Give it at least a quarter of an hour, as SerpentX’s verification procedure does. Solo CKPool, whose minimum difficulty is 10,000, can be slow to show a small share.
• Dual pool, on the machine. The NerdQAxe firmware shows each pool’s connection and its accepted and rejected shares. SerpentX publishes the poolASharesAccepted and poolBSharesAccepted counters in /api/system/info.
• That the solo pool really pays you. AxeOS 2.15 decodes the coinbase transaction in the work sent by the pool and warns if your share of the reward drops below 95%. Since 1.1.0, the NerdQAxe firmware checks that your address is in the coinbase transaction. With two pools, check both.

Nothing shows up anywhere? The usual causes (address, port, Wi-Fi) are in Bitaxe not hashing.

• Statistics cut in two. Each pool only sees the shares it receives: its hashrate curve gets noisier, and your best share there, the one leaderboards use, only reflects its part of the work.
• Losses at each switch. On SerpentX, an interval that is too short wastes work: according to its author, going from 500 to 3,000 milliseconds took the error rate shown by one of his miners from about 20% to about 3%. Keep the default. Almost every pool uses the same version-rolling settings; if the two differ, pool B may reject the odd share.
• Unofficial firmware. SerpentX has no backing from the Bitaxe team: check the model, keep the official files at hand, and never mix Bitaxe, NerdAxe and NerdQAxe files.
• An outage at home. A fallback pool is useless if your router or Wi-Fi goes down: both pools are lost at once, and AxeOS pauses the chip. An issue open since 7 September 2026 (number 1953) describes, on 2.14 versions, a chip that does not restart when the pool comes back, until the machine crashes and reboots by itself a few minutes later; on a newer development build it restarts on its own, but sometimes only after several minutes.
• SHA-256 pools only. Bitcoin and Bitcoin Cash, yes; a coin that uses another algorithm, no: the chip can only compute SHA-256.