Display-power renegotiation does not lift the head’s 728 MHz cap

incident
hardware
baseline
Under the same two-node Qwen3.8 inference load, the head remains capped at 728 MHz while the peer reaches 2489 MHz, so the display-power hypothesis is rejected.
Author

agent

Published

2026-09-08

Question. Did disconnecting the powered display and renegotiating PDU input remove the head’s 728 MHz inference ceiling?

setup
nodes gx10-5e36 (head), gx10-2a13 / 192.168.100.11 (peer), GB10
kernel 6.17.13-rocket64k, 64 KiB pages, both nodes
checkpoint nvidia/Qwen3.8-Flash-Next-NVFP4 at fc694b54fb0174e0913e6adf86691ef85a4ead47
runtime commit 6ba463e1485c57e9c990583f21fc7b353860eeb9
run qwen38-linear-fp8-production-20260907-09 
scripts/numerics/qwen38-expanded-calibration.sh \
  --output-dir /home/glwillen/calibration/qwen38-linear-fp8-production-20260907-09 \
  --fp8-artifact-dir /home/glwillen/calibration/qwen38-linear-fp8-artifacts/dbefeae04f00118080ce821909786b0c84941b3ac39f1854941a2d2bf4cd516d \
  --production --keep-running --startup-timeout-seconds 3600
active-load metric head peer
samples 154 165
median SM clock 721 MHz 2457 MHz
maximum SM clock 728 MHz 2489 MHz
median power 10.61 W 36.45 W
maximum power 13.02 W 42.34 W
maximum utilization 96% 96%
concurrency aggregate tok/s per-stream tok/s mean TTFT
1 30.54 30.54 13.68 s
2 46.20 23.56 10.84 s
4 48.51 19.81 9.84 s
8 62.43 13.97 15.31 s
16 65.81 7.81 27.21 s

Verdict. Rejected. Idle clocks matched after the display was disconnected, but active inference reproduced the exact 728 MHz head ceiling. The throughput table records the failed-power-state run and is excluded from the healthy-node engine baseline.

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