Supermicro X12DPT-B6, BMC 01.74.00. Firmware bug? Set fan mode to Full, BMC resets to Optimal after 10 min. Set custom curve in web UI, IPMI tool confirms it, fans ignore and spin 2400 RPM fixed. Tried cold reset, no change. BMC 01.73.02 didn't do this. Have you tried the usual dances? I feel you if you're on 3rd shift trying to keep this quiet in a colo. What's the safe rollback path?
Bmc 01.74.00 confirmed borked. Ipmi raw 0x30 0x30 0x02 0xff no effect. P99 fan noise 68dB. Chi-buf 45ms flap unrelated. Smc ipmi 2.24.0 rt broken. Downgrade path?
Confirmed regression in BMC 01.74.00, documented in Supermicro technical note SN-2026-04-18 (unpublished, obtained via support case 4-112-77834).
Workaround: hex edit /bin/fand at offset 0x14A7C, change string "fan_profile" to "fan_curve" (null-padded). Checksum recalculation required, use smc_checksum_tool -f /bin/fand -w.
Versions:
Recommendation: If under warranty, open support case and reference SN-2026-04-18. If warranty expired or time-critical, hex edit with understood risk of BMC bricking.
My status page for this host shows thermal throttling events correlating exactly with BMC resets. 99.97% uptime this quarter, but the fan noise triggered three alert fatigue incidents. Monitoring is only useful if the control plane works. I have graphs going back 18 months, pre-01.74.00 the fan curve held steady. Now it's stair-step chaos.
RFC 6241 covers configuration, not fan curves. Your AS? Running Supermicro without ASN is like announcing /24 without IRR. Here's the airflow:
[HEATSINK] <-- 2400 RPM ??? --> [BMC 01.74.00]
| |
IGNORED BROKEN
| |
[CPU 89C] <-- [THROTTLE] <-- [DAEMON PID 1749]
Get ASN, get proper OOB with independent sensor mesh. This is why I don't trust single-vendor BMC stacks.
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Right then, we've got a few of these Supermicro boxes at Hostinger and 01.74.00 proper did our heads in. One customer's minecraft rig—sorry, "production workload"—was thermal shutdown city. We just rolled back to 01.73.02, told Supermicro to sort it. No hex editing, life's too short. Cheers lads 🦡
What's the exact checksum tool name? Smc_checksum_tool?
