DGX Spark Benchmark Results: vLLM on SM121

Measured throughput and latency on DGX Spark GB10 (SM121) hardware. All results use vLLM 0.19.0 (NGC container nvcr.io/nvidia/vllm:26.04-py3) unless noted. Qwen3-235B-A22B-GPTQ-Int4 — Two-node cluster Date: 2026-05-03 Config: TP=2, EP=2, Ray cluster over QSFP-DD RoCE direct interconnect, --attention-backend=TRITON_ATTN, --quantization=gptq_marlin, --kv-cache-dtype=fp8, --gpu-memory-utilization=0.87 Batch Avg completion tokens tok/s per request Aggregate tok/s 1 (serial) 256 17.0 17.0 2 (concurrent) 256 12.1 24.1 4 (concurrent) 256 9.1 36.4 Prefix cache: 97% delta hit rate on repeated system prompt. Startup to first inference: ~15 minutes (Ray init + weight load across two nodes + compile). Weight resident per node: 57.64 GiB. ...

May 9, 2026 · 2 min · Conselara Labs

DGX Spark Model Comparison: What Fits and What Runs (SM121, 128 GB)

Quick-reference comparison of open-weight models for a single DGX Spark GB10 (SM121, 128 GB unified LPDDR5X memory). Based on tested configurations and community results as of May 2026. Model Architecture Quantization Memory Expected tok/s SM121 notes Qwen3.6-35B-A3B Pure MoE (3B active) FP8 (~35 GB) ✅ easily 100+ Pure MoE, no GDN — fully supported Qwen3.6-27B Dense hybrid (GDN) FP8 (~28 GB) ✅ easily 14–21 (stock) / 136–200 (fork) GDN kernel gap; experimental fork needed for full speed Qwen3-30B-A3B Pure MoE (3.3B active) NVFP4 / FP8 / BF16 (~16–60 GB) ✅ easily 32–50 Solid single-node option; no GDN gpt-oss-120b Sparse MoE (5.1B active) mxfp4 (~61 GB) ✅ 32–60 128K context; proprietary quant format Qwen3.5-122B-A10B Pure MoE (10B active) NVFP4 only (~75 GB) ✅ up to 51 BF16 is 234 GB — does not fit; NVFP4 is the only path Qwen3-235B-A22B Pure MoE (22B active) GPTQ-Int4 (~60 GB/node) ✅ (two nodes) 17–36 agg Requires two DGX Sparks; best quality available Qwen3.5-397B-A17B Pure MoE (17B active) NVFP4 (TP=2) ✅ (two nodes) Unknown SM121 MoE kernel not yet optimized; not recommended Key observations Throughput vs quality tradeoff at single-node: Qwen3.6-35B-A3B gives the highest throughput (100+ tok/s) with pure MoE architecture. Qwen3.5-122B-A10B gives the most capable model (10B active parameters) that fits on one node, at 51 tok/s. For most agentic workloads the bottleneck is tool latency, not token generation — so 51 tok/s is more than sufficient. ...

May 9, 2026 · 2 min · Conselara Labs

vLLM Model Selection for DGX Spark (SM121)

The DGX Spark GB10 SoC (SM121) has specific constraints that determine which models run well and which don’t. This is a practical guide based on what we’ve tested in production. The key constraint: SM121 kernel compatibility Not all model architectures run well on SM121 with the NGC vLLM container. The main constraint is the MoE kernel: Marlin kernel — stable, fast, supports GPTQ-Int4 and mxfp4 CUTLASS FP4 — broken on SM121, produces garbage outputs silently; never use GDN (GatedDeltaNet) — kernel gap on SM121, 14–21 tok/s with stock NGC; requires experimental fork for full speed Prefer pure MoE models over dense hybrid architectures when using the NGC container. Pure MoE (no GDN/Mamba layers) runs fully through Marlin and is well-tested on SM121. ...

May 9, 2026 · 4 min · Conselara Labs

Running Qwen3.5-122B on a Single DGX Spark

The NVIDIA DGX Spark (GB10 SoC, 128GB unified LPDDR5X memory) can run Qwen3.5-122B-A10B — a 122B parameter MoE model — at usable throughput for production workloads. Here’s what it actually takes. The key constraint: NVFP4 only Qwen3.5-122B-A10B at full precision is ~250GB. In NVFP4 quantization it’s ~75GB, which fits comfortably in 128GB unified memory. There is no other quantization path that both fits and runs correctly on the GB10. The only verified checkpoint we’ve found: bjk110/SPARK_Qwen3.5-122B-A10B-NVFP4 on HuggingFace, which includes 15 patches for the SM121 architecture. Use this; don’t try to quantize the base model yourself unless you’re prepared to debug SM121-specific kernel failures. ...

May 5, 2026 · 3 min · Conselara Labs