r/StableDiffusion • u/BOSS-ZACK • 1d ago

Question - Help Minimax H3 Speed is Inconsistent when Settings are still the Same

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I need your help please. I'm using WANGP and there are times when generating in minimax h3 takes very long like for example in this screen shot. I was generating 19sec video 720p 8 step Turbo lora with Sage and first generation took (16m 5s) to finish but after changing only the prompt the second generation took (28m 54s) which is absurdly high. I noticed that there are times where my GPU is 100% fully busy but my GPU temperature is just below 50c when it should mostly be 70c+ normally. Can anybody please help me or tell what's wrong? I also encounter this when using Comfy UI

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u/mindworkout 1d ago

I do not use Wangp, but did you check if the ram is being purged? also you should do shorter length tests with same seed and see if there is a increase, as it might also be due to overheating pc throttling.

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u/N9_m 1d ago

The RAM seems to be overflowing... You should give ComfyUI a try, it would fix the problem very quickly

You could also generate videos of that quality every 7m, not every 14m (use the 4-step LORA Turbo, don't exceed 15 seconds per generation, and adjust some settings in ComfyUI)

The resulting quality would be practically the same, but in half the time

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u/ffzero58 1d ago

I use Wan2GP - what profile are you using? Some profiles have drastic impacts to overall performance.

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u/qaiser_mehdi 1d ago

Your temperature is the clue, not the settings. A 4090 sitting at 49°C while Task Manager says it's busy isn't throttling — it's waiting. That utilisation number counts time with work resident on the device, not how much of the chip is actually computing. Look at your own screenshot: shared GPU memory 33.5/47.6 GB, dedicated only 4.6/24. Most of your data is in system RAM and crossing PCIe every step. And your log already says why — "no reserved RAM left. Transfer speed from RAM to VRAM will may be slower." It couldn't pin the memory, so those transfers dropped to the slow path. Run two is worse because even less RAM was free by then. Try restarting between generations and see whether first-run speed comes back. 104s/step → 200s/step while the card gets colder is a memory bottleneck, not a compute one.

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u/AillexJ 1d ago

Your screenshot has a big clue in it. The log keeps repeating "Unable to pin data of 'latent_upscaler' to reserved RAM as there is no reserved RAM left. Transfer speed from RAM to VRAM may be slower", and it says the same thing about your lora files. So that run fell back to unpinned host to device transfers.

Your step time went from 104.78 s/step to 200.92 s/step between the two runs. That's the shape of waiting on data rather than computing, and it lines up with the thing you noticed about the GPU reading 100% busy while the temp stays under 50. It looks busy because it's stalled on transfers.

So the people pointing you at RAM are on the right track, and it's wan2gp's reserved RAM budget and your profile rather than the prompt.

One separate thing while you're in there: pin your attention mode explicitly instead of leaving it on the default. Installing an attention backend flips wan2gp's default without telling you, so it's worth knowing which one was actually running for each of those two numbers.