Whatsminer M60S – Firmware Signature Verification Failed

Power-cycle at the PDU and wait five minutes. Do NOT hit Upgrade again immediately. A small subset of signature-verification events are transient (network hiccup mid-read of a signed payload, verifier state machine wedged) and clear on a clean cold boot. If the error returns, this is a persistent signature problem — move to Tier 2. Do not repeat more than twice; every retry on a persistent signature error raises hard-brick risk.

Photograph the chassis label and the MinerTool error line before doing anything else. Record sub-model (M60S vs M60S+ vs M60S++), serial, firmware version last known good, exact error code displayed, LED state. These five facts drive every recovery decision below. Operators who skip this step flash the wrong file two hours later and hard-brick the unit.

Download the MicroBT-official firmware image and its published SHA-256 from `support.whatsminer.com`. Match sub-model exactly. Compute the file's SHA-256 locally (`sha256sum` on Linux/macOS, `CertUtil -hashfile file.bin SHA256` on Windows). Must match byte-for-byte. If not, re-download and clear the browser cache — never flash an unverified file on an M60S.

Attempt a MinerTool recovery-mode flash. Cold-boot the miner, catch it in the 30-60 second bootloader window, push the verified image via WhatsminerTool V9.0.1 → Firmware Upgrade. Do not interrupt, do not walk away, do not batch this with 39 other miners — this is a single-unit recovery. Success = miner reaches 100%, reboots clean. Failure = flash aborts or miner reboots to same error.

Prepare an SD recovery card. Grab a microSD (8-16 GB, SanDisk Ultra or Samsung EVO — not a no-name card). Download MicroBT's recovery image for your exact sub-model. Flash with `balenaEtcher`. Do not rename, do not repartition, do not attempt to fit a Bitmain image on an M60S — different chip family, different boot chain, different signing tree entirely.

Open the chassis for SD recovery. PDU off, five-minute cap-drain, six Torx `T20` screws on the top cover. Locate the control-board microSD slot (near the Ethernet jack, silkscreen `SD`). Seat the prepared card firmly. Reassembly is optional during recovery — the miner won't hash until recovery completes, so airflow isn't yet a concern.

Execute SD-card recovery. Re-connect PDU. Power on. The control board auto-detects the SD on boot and re-flashes the user-writable partitions. Typical recovery takes 8-12 minutes. LED sequence: solid-red → slow-red-blink → alternating red-green → solid-green. If solid-red persists past 15 minutes, power off, re-seat, try once more. If the second attempt fails, escalate to Tier 4.

Remove the SD card and normal-boot. Critical step operators forget: after recovery succeeds, power off, pull the SD, close the chassis, normal boot. Leaving the card in causes the miner to loop recovery on every reboot — not broken, but wastes flash cycles and clutters your ops. Validate hashrate stabilizes at nameplate within 15 minutes.

Connect a USB-UART console to the control board. Use a `3.3 V` USB-UART adapter (FT232RL, CP2102, or CH340 with `3.3 V` jumper — NEVER `5 V` on the M60S debug header, you will kill the SoC). Wire `GND→GND`, `TX→RX`, `RX→TX`. Terminal at `115200-8-N-1` (PuTTY, picocom, `screen /dev/ttyUSB0 115200`). Capture the boot log at power-on.

Interpret the boot log. `ROM: secure boot fail` at stage 0 = first-stage signature or OTP mismatch (Tier 4, ship it). `BL1 OK, kernel verify fail` = mismatched kernel/rootfs pair (re-flash the matching set). `FUSE: rollback counter n < m` = rollback fuse blocked the downgrade (use a newer build or Tier 4). `eMMC read error` = storage failure, Tier 4. Any `panic` not prefixed with a signature keyword = different error class, stop and re-diagnose.

Bench-flash via USB-to-eMMC adapter (experienced only). If serial console confirms user-writable-partition corruption but secure-boot ROM is healthy, the eMMC can be pulled via hot-air BGA rework or image-written in-circuit via factory test pads. Deep-bench work — correct flux, preheat profile, image for the correct sub-model, patience. Wrong procedure kills the control board. Budget 2-4 hours if experienced; if not, don't.

Verify flashing with a clean boot and hashrate validation. After any bench flash: boot with MinerTool attached, watch serial console, then verify API responds on TCP `4028`, hashrate stabilizes within 15 minutes at your configured power target, `power.log` shows no PSU faults, per-chain temps are normal. A successful flash that hashes at 40% of nameplate is still broken — signature chain is necessary, not sufficient.

Know when to stop. Serial console reports `ROM: secure boot fail` or `FUSE: rollback counter` after SD recovery attempts; control board shows physical damage; bench-flash returned a signature error on a verified-correct image. OTP-fuse / manufacturer-JTAG territory — no path forward without MicroBT-internal fixtures. Continuing DIY actively makes things worse; each retry in a half-flashed state can corrupt additional partitions. Stop and book D-Central repair.

D-Central bench process: controlled power-up on known-good PSU load, full serial-console capture from power-on, eMMC image validation against MicroBT's published signing tree, control-board swap from graded M6x inventory when OTP is confirmed damaged, post-repair 24-hour burn-in at nameplate. For JTAG-only units (confirmed OTP corruption), we coordinate RMA paperwork with MicroBT's North American distributor network — cross-border handled routinely.

Disclose custom-firmware history up front. If you flashed Vnish, Asicdip, or any 'unlocked' image before hitting this error, tell the bench. The fix path differs materially from a factory-firmware downgrade failure, and withholding history wastes diagnostic time (and your money). Mining Hacker code: tell the bench what actually happened. Every repair shop in the industry appreciates this.

Ship safely. Anti-static bag minimum; double-box with ≥5 cm foam on all sides; if shipping the whole chassis, remove the PSU and pack separately to reduce impact load on control-board standoffs. Include a note listing sub-model, serial, last-known-good firmware version, what you flashed, what errors you saw, what recovery attempts you made. That note saves 45 minutes of diagnostic time — saves you `CAD $75+` on the invoice.