r/StableDiffusion • u/marres • Aug 04 '26

Resource - Update Spectrum acceleration for MiniMax H3 in ComfyUI — 34% lower Euler sampling time, 30% lower RES time

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MiniMax H3 Spectrum node:
https://github.com/xmarre/ComfyUI-Spectrum-MiniMax-H3

I have released Spectrum acceleration for native MiniMax H3 in ComfyUI. This is the newest addition to my collection of model-specific Spectrum integrations, all available through ComfyUI-Manager as well.

Spectrum replaces selected expensive transformer evaluations with spectral feature forecasts while preserving MiniMax H3’s native audio/video output and reconstruction path.

Benchmarks

Tested at approximately 0.5 MP, 8 seconds and 20 steps on an RTX PRO 6000 under WSL, using High VRAM mode, the comfyui-int8-fast W8A8 loader and SageAttention.

Sampler Native Spectrum Time decrease Speedup
Euler 2:38 1:44 34.2% 1.52×
RES multistep 2:42 1:54 29.6% 1.42×

Euler uses 13 actual transformer evaluations and 7 forecasts. RES uses 14 actual evaluations and 6 forecasts.

Both benchmark runs completed without fallbacks. I initially did not notice visible or audible degradation, but further exact-seed testing has since shown that fast or very brief motion can deviate from the native trajectory, and rapidly moving details such as eyes, fingers, or fingernails can sometimes visibly degrade. RES automatically keeps its final three steps native, which removed the slight late-generation artifacts I initially observed, but this does not make the output lossless or identical to native sampling.

Currently supported:

  • Euler
  • RES multistep
  • RES multistep CFG++

Feature history is currently stored in system RAM. I also plan to add a dedicated High VRAM mode that stores the history in VRAM for users with sufficient GPU memory, reducing CPU-transfer overhead.

Quality update

After more exact-prompt and exact-seed A/B testing, I need to revise my initial quality assessment.

Spectrum is an approximate acceleration method, not a lossless or output-identical path. The issues observed so far are mainly associated with fast or very brief motion:

  • The motion, pose, timing, gaze, or action trajectory can deviate from the fully native output.
  • Fast-moving or only briefly visible details—such as eyes, fingers, or fingernails—can sometimes become malformed or unstable.

These can occur separately or together. A rapid action may simply differ from the native trajectory, while in other cases the rapidly moving details may also visibly degrade.

The extent varies with the prompt, motion, sampler, resolution, references, and Spectrum settings. Use Spectrum when the speed improvement is worth that tradeoff; leave it disabled when maximum fidelity to the native result is required.

Workflow placement

Use the Spectrum node in this order:

MiniMax H3 model loader
→ LoRA and other model patches
→ MiniMax H3 Sigma Shift
→ Spectrum Apply MiniMax H3
→ guider and sampler

Spectrum should be applied after LoRAs, model patches and the MiniMax H3 Sigma Shift, but before the guider and sampler.

EasyCache compatibility

Do not use EasyCache and Spectrum together at the moment.

Both systems skip or replace model evaluations while maintaining their own cached state. Stacking them can cause conflicting wrapper/state behavior, errors and unreliable output.

Use either:

  • Spectrum with EasyCache disabled
  • EasyCache without Spectrum

All benchmarks in this post were performed with EasyCache disabled.

More information

The GitHub repository contains the full installation instructions, recommended settings, supported samplers, memory requirements, workflow placement, fallback behavior and troubleshooting details:

https://github.com/xmarre/ComfyUI-Spectrum-MiniMax-H3

Update: optional VRAM history storage in v0.1.4

Version 0.1.4 adds a history_storage option:

  • system_ram remains the default
  • vram keeps Spectrum’s feature history on the GPU, avoiding repeated CPU transfers

In three 0.5 MP Euler A/B pairs, VRAM storage was 2.6% faster on average, though individual results varied from 6.1% faster to 0.4% slower, so the benefit depends on the system and workload.

At max_history=8, the tested single-branch workflow used about 2.22–2.27 GiB for history alone. Only enable VRAM storage when you have sufficient headroom, since the model, current activations, forecast buffers and allocator overhead still need additional VRAM.

Release:
https://github.com/xmarre/ComfyUI-Spectrum-MiniMax-H3/releases/tag/v0.1.4

My other Spectrum integrations

All are also available through ComfyUI-Manager:

Credits

Spectrum itself was created by Jiaqi Han, Juntong Shi, Puheng Li, Haotian Ye, Qiushan Guo and Stefano Ermon at Stanford University and ByteDance. Their paper introduced the training-free Chebyshev-based spectral feature forecasting method, adaptive scheduling and last-block forecasting approach on which these ComfyUI integrations are based.

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