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license: apache-2.0
tags:
- benchmark
- llm-inference
- mixture-of-experts
- tensor-parallelism
- consumer-gpu
- freetoken
- qwen
pretty_name: FreeToken Qwen3.6-35B-A3B Dual RTX 3090 Benchmarks
FreeToken Qwen3.6-35B-A3B — Dual RTX 3090 Consumer Benchmarks
Measured inference performance of Qwen3.6-35B-A3B (FP8 / NVFP4 / BF16 checkpoints) served by FreeToken on a consumer dual-GPU workstation (2x RTX 3090 24 GB, 62 GB RAM), across quantization formats, tensor-parallel configurations, MoE backends, RAM bandwidth regimes, and three engine revisions — including validation of two upstream fixes that landed during testing.
This is, to our knowledge, the first published set of consumer dual-GPU numbers for this stack. All figures were measured on real hardware; methodology and provenance below.
Hardware / software environment
| Component | Value |
|---|---|
| GPU | 2x NVIDIA RTX 3090 24 GB (Ampere, sm_86), PCIe |
| CPU | Intel Core i9-10980XE, 18c/36t (X299 platform) |
| RAM | 62 GB DDR4, tested at 2000 MT/s (JEDEC) and 3600 MT/s (XMP) |
| OS | Ubuntu 24.04 |
| Driver / CUDA | 580.173.02 / CUDA 13.0 (official toolkit — see reproduction notes) |
| NCCL | 2.31.2 (libnccl2 + libnccl-dev) |
| Engine | FreeToken v0.1.2 (PyPI) + freetoken_kernel_cache 0.1.2+cu130; later PR #104 head 3c8b281 + stacked branch (f1ff8e2, then c23ec78) |
| Models | nvidia/Qwen3.6-35B-A3B-FP8 (35 GB), nvidia/Qwen3.6-35B-A3B-NVFP4 (22 GB), BF16 (~70 GB, OOM on this host) |
Headline findings
1. Config ladder (decode throughput, tok/s)
| Config | Engine revision | Decode tok/s | Verdict |
|---|---|---|---|
| FP8, TP=1, offload | v0.1.2 | 93.9 | Speed champion on 2x 3090 |
| NVFP4, TP=1, hybrid | v0.1.2 | 61.0 → ~79 (RAM 3600 MT/s) | CPU/RAM-bound |
| NVFP4, TP=2, hybrid | PR #104 @ f1ff8e2 |
2.2 | Broken: CPU executor core collision |
NVFP4, TP=2, hybrid + --moe-cpu-threads 8 |
PR #104 @ f1ff8e2 |
9.5 | Workaround (4.3x) |
| NVFP4, TP=2, offload | PR #104 @ f1ff8e2 |
3.1 | PCIe + host all-reduce serialization |
| NVFP4, TP=2, hybrid | PR #104 @ c23ec78 |
32.7 wall / 59.3 engine-instantaneous | Affinity fix verified: 14.9x vs broken |
| FP8, TP=2 | PR #104 @ f1ff8e2 |
— | OOM at load (62 GB RAM < ~35 GB banks + runtime) |
| BF16, TP=2 | PR #104 | — | OOM (67 GB model > 62 GB RAM) |
2. KV-cache capacity is the real TP=2 prize
| TP | Usable KV tokens |
|---|---|
| 1 | 262,144 |
| 2 | 524,288 (2.4x claim confirmed) |
3. RAM bandwidth scaling (2000 → 3600 MT/s)
| Metric | 2000 MT/s | 3600 MT/s | Change |
|---|---|---|---|
| CPU STREAM read | 54.1 GB/s | 80.8 GB/s | +49% |
| PCIe H2D | 8.6 GB/s | 8.5 GB/s | flat |
| CPU-MoE NVFP4 | 28.1 GB/s | 46.7 GB/s | +66% |
| CPU-MoE BF16 | 41.5 GB/s | 71.3 GB/s | +72% |
| Serving: NVFP4 hybrid decode | 60.1–63.8 tok/s | 76.0–80.9 tok/s | +29–31% |
| Serving: FP8 offload decode | ~90–106 tok/s | ~86–106 tok/s | flat (PCIe-bound) |
Lesson: RAM overclocking only pays off on CPU-compute (hybrid) MoE paths; pure offload is PCIe-bound.
4. Engine findings reported upstream (PR #104)
- CPU executor core collision (fixed in
c23ec78): both TP ranks' hybrid executors pinned to the same physical cores. Per-rank disjoint core partitioning recovered 13.5–14.9x across three independent machines (this dataset's host + two author machines). - Offload +
--disable-pyncclserialization: in offload mode, per-token PCIe expert streams and the host-staged all-reduce contend on the same bus. Machine-dependent: hybrid wins on bare metal, offload can win in VMs. - Fused MoE gate (
freetoken/engine/engine.py,applied_nv/applied_fpguards):--moe-backend fusedrefuses NVFP4/FP8 ("bf16-only for now"). At TP=2 the sharded NVFP4 experts (~11 GB/rank) would fit in 24 GB of VRAM — lifting this gate would likely beat every row in this dataset.
Also verified: the lm_head vocab-sharding fix (f1ff8e2) — both FP8 and NVFP4 now load past the previous
crash point at TP=2.
Data
benchmarks.jsonl — one row per measurement. Schema:
| Column | Type | Meaning |
|---|---|---|
date |
string | Measurement date (UTC) |
engine |
string | FreeToken version / commit |
model |
string | Checkpoint served |
quant |
string | fp8 / nvfp4 / bf16 |
tp_size |
int | Tensor-parallel size |
moe_backend |
string | offload / hybrid / n/a |
attention_backend |
string | e.g. hybrid_linear, triton |
extra_flags |
string | Non-default serve flags |
ram_mts |
int | DDR4 transfer rate during run |
category |
string | serving / bandwidth / capacity / load_test |
metric |
string | decode_tok_s, ttft_s, bandwidth_gbs, kv_usable_tokens, load_status |
target |
string | For bandwidth rows: the subsystem measured |
value |
number/string | Measured value (or status string) |
value_max |
number | Upper bound when the run produced a range |
unit |
string | Unit of value |
notes |
string | Context, caveats, cross-references |
Methodology
- Serving numbers: OpenAI-compatible endpoint (
127.0.0.1, local), scripted client, representative prompt batches (up to 399 output tokens); decode throughput = generated tokens / decode-phase wall time unless noted (engine-instantaneous= the server's own logged per-batch gen throughput). - "Warm" = after first request; "cold" includes FlashInfer JIT compilation.
- Bandwidth rows:
ft bench bwcalibration output. - Every TP=2 row was run on an otherwise idle host; a contaminated first offload measurement (a stale server holding both GPUs) was discarded and re-run clean — the discarded number is not in this dataset.
Reproduction notes (the parts the docs understate)
- Do not use pip-installed CUDA packages with FreeToken. FlashInfer JIT-compiles kernels lazily
(including at first inference), so a partial toolkit fails after the server reports ready. Install the
official toolkit:
cuda-nvcc-13-0 cuda-cudart-dev-13-0 libcurand-dev-13-0,CUDA_HOME=/usr/local/cuda-13.0. - Multi-GPU needs NCCL dev libs:
sudo apt-get install libnccl2 libnccl-dev(upstream docs PR #90). - After killing
ft serve, orphaned multiprocessing workers can hold VRAM and port 1920;pkill -9 -f "multiprocessing.spawn"cleans them. - DDR4-3600 stability on X299 quad-channel may need VCCSA/VCCIO raised (1.2 V / 1.15 V worked here) — vdimm alone at 1.35–1.41 V was not sufficient.
bench_decode_moe.py(upstream) hangs spawning its own server in this environment; directft serve+ scripted client was used instead.
Provenance
- Engine: FlashML-org/FreeToken
- TP support work: PR #104 (+ stacked branch by CraigStone-Dev)
- Tracking issues: #29 (Qwen3.5/3.6 MoE TP=1 gate), #15 (multi-GPU roadmap)
- Benchmarks and fix validation on this hardware: Alogotron
Limitations
- Single hardware sample (Ampere consumer); NVFP4 carries a software-dequant penalty here — Blackwell cards should shift the hybrid/offload balance.
- Decode figures are single-client, moderate batch; no concurrency sweep.
- BF16 rows are load-test only (host RAM bound).
Citation
@misc{freetoken_qwen36_dual3090_benchmarks,
title = {FreeToken Qwen3.6-35B-A3B — Dual RTX 3090 Consumer Benchmarks},
author = {Alogotron},
year = {2026},
url = {https://huggingface.co/datasets/Alogotron/freetoken-qwen36-dual3090-benchmarks}
}