Cheapest viable deployment: 2x MI300X beats 2x H200 by ~4x — plus, any plan for Dynamic GGUFs?

#1
by guitaripod - opened

Sharing numbers in case they save someone else the research, and one question at the end.

The memory budget. The FP4+FP8 checkpoint is ~158 GB. With FP8 KV cache the full 1M context only adds ~10 GB (V4 uses roughly 7% of V3.2's KV footprint), so the realistic floor is ~170-175 GB of VRAM for a single replica. That rules out one 192 GB card if you want real context headroom, and makes 2x anything-with-192GB the natural unit.

What that costs per hour, on-demand:

  • 2x MI300X (384 GB total): $3.00-4.00/hr on-demand ($1.99/GPU at DigitalOcean/Hot Aisle), ~$3.00/hr on RunPod spot at $1.49/GPU
  • 2x H200 SXM (282 GB total): ~$7.18/hr on RunPod
  • 4x A100 80GB (320 GB total): usually lands between the two, and you eat the older interconnect

The 4x A100 recommendation that gets repeated everywhere is a tensor-parallel artifact — TP prefers power-of-two GPU counts, and 2x A100 at 160 GB falls just under the budget, so the next legal step is 4x. It is not a real hardware requirement.

What I run on the MI300X pair:

vllm serve unsloth/DeepSeek-V4-Flash-0731 \
  --tensor-parallel-size 2 --enable-expert-parallel \
  --kv-cache-dtype fp8 --gpu-memory-utilization 0.92 \
  --max-model-len 262144 --host 0.0.0.0 --port 8000

262K rather than the full 1M — Think Max wants 384K minimum, and dropping the cap is the cheapest knob for batch headroom. vLLM and SGLang both had day-0 support and read the native FP4/FP8 checkpoint directly, no conversion step.

The honest caveat nobody putting up a deployment guide wants to write. First-party API is $0.14/M input, $0.28/M output, and $0.0028/M on cache hits. Against a blended ~$0.18/M, a $3/hr box needs somewhere around 400M tokens/day at genuine full utilization to break even — and no real workload sustains 100% GPU utilization. Self-hosting this model is a privacy, latency, or data-residency decision. It is not a cost decision unless you are saturating the box around the clock. Worth saying out loud, because the cost framing is what most self-host posts lead with.

The question: any plan for Dynamic 2.0 GGUFs of this checkpoint? Upstream llama.cpp does not handle the V4 architecture yet (CSA + HCA attention, mHC), so I assume the blocker is there rather than on your side — but if UD quants are on the roadmap it changes the calculus a lot for people with 2x 96 GB consumer-adjacent cards or a big unified-memory box, who currently have no path at all. A ~70-80 GB UD-Q2/Q3 would open up a tier of hardware that is completely locked out today.

Thanks for mirroring these so fast either way.

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