howtospark
models / XHToken/Spark-X2.5-4B-Base
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4.1B paramsbfloat16GQA 16:41.0M ctxapache-2.0
Sparks
~21 GB
~19 GB
~17 GB
~15 GB
~14 GB
110 usable
Spec decode
Context33K / 1.0MKV
On the Sparks — 1× · 1-bit GGUF (dynamic) · 33K ctx · FP16 KV~684K ctx fits usable
spark
96 GB free
110 usable
14* / 110 GB
13% of usable
Dense 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
36 layerssliding window×27full attention×9
in
out
all 36 layers fire per token — 4.1B active
Optimize
Verdict

4B params, ~8 GB at bfloat16 — fits on one Spark as-is.

Make it fit

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

Lossless compression

BF16 weights entropy-code ~30% smaller bit-exact — smaller downloads and less bandwidth per token, no quality question at all.

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 ~33.2 tok/s ceiling; a trained EAGLE-style draft multiplies tokens per weight-read.

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.