S11 Fan-Inversion Fix

A free, verifiable one-shot repair for Innosilicon S11 miners whose fans run backwards. Published by the pool for every S11 owner, whether you mine here or not.

Download s11-fan-fix.sh

Is your unit affected?

Fans are loud when cold or idle and get quieter as the unit heats up.
The dashboard reports a low fan duty (10%) while the fans are clearly screaming: the number is the inverse of the real airflow.
Chip temperatures climb higher than expected under load.

If the fans already speed up as the unit heats, your board is not affected. Running the tool anyway is harmless: it detects healthy binaries and changes nothing.

What it does

The firmware computes speed = 100 − speed in both fan controllers (cgminer and dm-monitor). The fix replaces that one CPU instruction with a no-op in each, over the network, then reboots the unit. The exact on-device script is embedded in full and commented inside the download; read it before you run it.

Self-verifying: it reads the exact bytes first and patches only if it finds the exact buggy instruction. Anything unexpected aborts with no changes.
All-or-nothing: copy, patch the copy, byte-verify, then an atomic rename. Never writes a running program in place.
Idempotent: a fixed unit reports "already patched".

Download and verify

The checksum below is computed from the file this server hands out. Compare before you run anything.

File	Version	Size	Updated
s11-fan-fix.sh	—	—	—

SHA-256

computing…

Linux / macOS

curl -fLO /tools/s11-fan-fix.sh && curl -fLO /tools/s11-fan-fix.sh.sha256
sha256sum -c s11-fan-fix.sh.sha256      # macOS: shasum -a 256 -c s11-fan-fix.sh.sha256
chmod +x s11-fan-fix.sh

Requires only a POSIX shell, curl and od; nothing to install. Windows: run it from WSL.

Run it

From any computer on the same LAN as the miner. You need the miner's IP and its admin web password.

Run the tool against the miner's IP
shell
```
./s11-fan-fix.sh 192.168.1.170
# non-default admin password:
./s11-fan-fix.sh 192.168.1.170 my-admin-password
```
Without a password it tries the common defaults (admin, dragonadmin). S11_USER / S11_PASS work as environment variables too.
It logs in, patches, byte-verifies, and reboots the unit
DO NOT CUT POWER! Give it 30 to 60 seconds to come back. A failed run aborts before committing anything and prints why.
Watch the fans under load
They should now speed up as the chips warm. Reported duty and real airflow agree from here on. Safe to re-run any time.

Stock firmware (recovery)

The factory image, served from our snapshot host with its checksum. Re-flashing it through the miner's own web UI restores the original binaries and is the reliable way back if a unit misbehaves after any change.

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Use at your own risk

Read this before running anything.

This software is provided as is, without warranty of any kind. P2Block is not liable for damage, downtime, hardware failure, voided warranty or any other loss.
You are modifying miner firmware. Only run it on units you own and are authorized to modify; it may void the manufacturer warranty.
It targets one S11 firmware build. On any other build it aborts without changes.
Have a recovery path ready: the stock firmware .swu above, re-flashed through the miner's own web UI, restores the factory binaries.
The same admin web interface that lets this tool work lets anyone on your LAN take the unit over. Change the admin password and keep miners on an isolated network segment.

Mining BTCB2 with your S11?

Every payout on this pool is a coinbase output you can verify on chain.

Point it at stratum+tcp://us1.p2block.com:3333 for the hosted tier, or run your own gateway for the lower fee. Start difficulty on port 3333 suits the S11 out of the box.

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