howtospark
models / nex-agi/Nex-N2.5-Pro
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397B params~19B activecompressed-tensorsMoE 512×10GQA 32:2262K ctxmultimodalapache-2.0
Sparks
~409 GB
~210 GB
~126 GB
~120 GB
~114 GB
110 usable
REAP dialno pruning · 512 experts
Spec decode
Context33K / 262KKV
On the Sparks — 1× · 2-bit experts + NVFP4 dense · 33K ctx · FP16 KV~0 ctx fits usable
spark
Expert planes96.2* GB2-bit
110 usable
+4 over
114* / 110 GB
104% of usable
Expert planesDense weightsKV cacheActivations + graphsOS reserve

* segment sizes marked with an asterisk are estimates pending a measured run

Estimated per-node footprint, weights + KV sharded across the Spark (tensor parallel). Overhead ~8 GB/node; KV at FP16.

layer map
60 layerslinear attention×45full attention×15
in
out

one MoE layer · 512 experts, 10 fire per token · showing 256

each expert ≈ 13M params

resident: 60 MoE layers × 512 experts × 13M 384.9B

active/token: 60 × 10 × 13M 7.5B experts

+ 11.9B always-on dense (attention, embeddings, shared stack) = 19.5B active

Optimize
Verdict

397B params, ~397 GB at already compressed-tensors-quantized and still ~198 GB at 4-bit — one Spark can't hold it; you need surgery or more Sparks.

Make it fit

Get the weights (and headroom for KV) inside the 128 GB pool — the hard gate.

Prune experts (then quantize)

With 512 routed experts and only 10 firing per token, REAP-style pruning cuts total params without touching active compute (params include vision/audio towers).

pruning to half the experts ≈ halves the routed-expert weights, ~109 GB at 4-bit

Split or stream it

Even 4-bit is ~198 GB against a 110 GB usable budget; shard across ≥2 Sparks or stream cold weights from NVMe.

Go below 4 bits

Codebook/outlier methods reach 2–3 bpw when 4-bit still overflows. — for MoE, the proven shape is a 2-bit sign-symmetric codebook on the routed experts with the dense stack kept at FP8 (vLLM-Moet).

~108 GB with 2-bit experts + FP8 dense (est.)

Make it fast

Once it fits: fewer bytes per token and fewer decode steps against 273 GB/s.

Add a speculative decoder

Decode is bandwidth-bound at ~28.1 tok/s ceiling; a trained EAGLE-style draft multiplies tokens per weight-read.

Tame the KV cache

At 262144 tokens the KV cache alone is ~32 GB at FP16; quantize or evict.

Make it yours

Change what the model does — adapt, edit, or steer it — independent of size.

Fine-tune it

LoRA/QLoRA adapts behavior on one Spark without touching the base weights.