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Open-weight model · Text generation

Qwen3.5-4B-DFlash2

by Nick Chapman nchapman/Qwen3.5-4B-DFlash2

Qwen3.5-4B-DFlash2 is an open-weight model for text generation from Nick Chapman. It has 662M parameters. At 16-bit it needs about 1.6 GB of GPU memory, which fits on 1x MI300X from $1.85 an hour, at the lowest prices in the SAVRN Index.

DFlash2 speculative drafter for Qwen/Qwen3.5-4B. selected at the serving temperature.

Parameters662M
Context—
Weights1.3 GB
License—
AccessOpen weights
Monthly Downloads—

Runs On

What it takes to serve Qwen3.5-4B-DFlash2 (662M parameters): the memory its weights need at each precision, and the cheapest way to rent enough data-center GPUs to hold them.

PrecisionWeightsMemory neededCheapest setupPer hourAlso fits
16-bit 1.3 GB 1.6 GB 1x MI300X (192 GB)
Vultr
$1.85 1x H100 $1.99 · 1x MI325X $2.00
8-bit 0.7 GB 0.8 GB 1x MI300X (192 GB)
Vultr
$1.85 1x H100 $1.99 · 1x MI325X $2.00
4-bit 0.3 GB 0.4 GB 1x MI300X (192 GB)
Vultr
$1.85 1x H100 $1.99 · 1x MI325X $2.00

Memory is the weights at that precision plus 20% for the runtime and a short context; a long context needs more. Prices are the lowest on-demand hourly rates in the SAVRN Index, read Oct 18, 2026.

Qwen3.5-4B-DFlash2 on every accelerator the SAVRN Index prices, at every precision

Model Card

DFlash2 speculative drafter for Qwen/Qwen3.5-4B. selected at the serving temperature. Beats the model's native MTP by ~+1 τ at every temperature in every measured config, and drafts against the bf16 base as well as against the W4A16-GPTQ quant it was trained on. run-to-run spread (t=1.0 is heavy-tailed: 0.34 observed on identical inputs; t=0.7 spread ~0.1). Numbers above are reported with n and ranges, never as single draws. Ranking is temperature-dependent — see Selection. All six epochs' checkpoints were ranked at three temperatures with repeats. At the serving point (t=0.7 — the same sampling config the training corpus was generated with, temp 0.7 / topp 0.95 / topk 20), τ rises…

Excerpt from the card by Nick Chapman.

Configuration

Architecture
DFlash2DraftModel

Identity and Version

Repository
nchapman/Qwen3.5-4B-DFlash2
Publisher
Nick Chapman
Task
Text generation
Modality
Text
Library
speculators
Parameters
662M parameters
Languages
Not stated by the source
Revision
84a8c4bdf99f44ca17ef3669334358ae30701e4d
First published
2026-10-14
Last updated
2026-10-14

Files and Weights

9 files, 1.3 GB in total. The weights are 1 file totalling 1.3 GB in safetensors.

Weights1 file · 1.3 GB
Configuration5 files · 5.2 KB
Documentation1 file · 3.0 KB
Other1 file · 616 B
Repository1 file · 1.5 KB
Every file
FileTypeSizeSHA-256
model.safetensorsWeights1.3 GB c919a019f84c
config.jsonConfiguration2.0 KB —
config.pyConfiguration1.4 KB —
run.yamlConfiguration536 B —
training_state.jsonConfiguration52 B —
val_metrics.jsonConfiguration1.2 KB —
README.mdDocumentation3.0 KB —
train_command.txtOther616 B —
.gitattributesRepository1.5 KB —

License and Download

License
Not stated by the source
Access
Open weights, no gate
Download size
1.3 GB
Download from Nick Chapman

Released by Nick Chapman through its official repository on Hugging Face.

Built From

Memory Requirements

PrecisionWeights in memory
As published1.3 GB
16-bit1.3 GB
8-bit0.7 GB
4-bit0.3 GB

Weights only, from the published parameter count; the key-value cache and runtime add to this.

Questions About Qwen3.5-4B-DFlash2

How much GPU memory does Qwen3.5-4B-DFlash2 need?

About 1.6 GB at 16-bit and 0.4 GB at 4-bit: the weights (662M parameters) plus a working margin. A long context needs more.

What is the cheapest GPU to run Qwen3.5-4B-DFlash2 on?

At 16-bit, 1x MI300X from $1.85 an hour; at 4-bit, 1x MI300X from $1.85 an hour, at the lowest on-demand prices the SAVRN Index lists.

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