Short answer: choose L40S when a qualified server needs 48GB, Ada-generation inference/media capabilities, vGPU support or display outputs. Choose A100 80GB when the measured workload genuinely crosses 48GB or needs A100’s MIG/interconnect ecosystem. A100 40GB has more published HBM bandwidth but less capacity than L40S; it is not automatically the better local-AI choice.
The decision in one minute
- L40S 48GB: Ada, compute capability 8.9, 48GB GDDR6 ECC, 864GB/s, 350W, passive server cooling, display and media engines, no MIG or NVLink.
- A100 40GB PCIe: Ampere, capability 8.0, 40GB HBM2, 1,555GB/s, 250W, passive accelerator, MIG and supported NVLink configurations, no display or NVENC.
- A100 80GB PCIe: 80GB HBM2e, 1,935GB/s, 300W passive accelerator; the only option here that changes the 48GB capacity ceiling.
- A100 SXM: a 40GB/80GB module for compatible HGX/DGX systems—not a low-cost substitute for a PCIe card.
L40S vs A100 specifications
| Hardware | Architecture / capability | Memory / bandwidth | Power | Platform features |
|---|---|---|---|---|
| NVIDIA L40S | Ada / 8.9 | 48GB GDDR6 ECC / 864GB/s | 350W | Passive PCIe server card; display outputs; NVENC/NVDEC; no MIG/NVLink |
| A100 40GB PCIe | Ampere / 8.0 | 40GB HBM2 / 1,555GB/s | 250W | Passive PCIe accelerator; MIG; no display/NVENC |
| A100 80GB PCIe | Ampere / 8.0 | 80GB HBM2e / 1,935GB/s | 300W | Passive PCIe accelerator; MIG; no display/NVENC |
| A100 40GB/80GB SXM | Ampere / 8.0 | 40GB HBM2 / 80GB HBM2e; 1,555 / 2,039GB/s | 400W | SXM module for compatible HGX/DGX; MIG and NVLink/NVSwitch platform |
L40S and A100 target server deployments, but their feature emphasis differs. L40S combines Ada inference, graphics and media capabilities with vGPU support. A100 is a compute accelerator with MIG and stronger scale-up options in supported systems. Licensing, supported profiles, system qualification and the exact software release remain separate purchase requirements.
Exact Qwen3.5 file-size boundaries
These margins subtract decimal file totals from nominal decimal device memory. They omit KV cache, hybrid-attention state, vision processing, allocator behavior and temporary buffers. Treat tight positive margins as warnings, not fits.
| Artifact | Files | A100 40GB | L40S 48GB | A100 80GB |
|---|---|---|---|---|
| Qwen3.5-35B-A3B Q8_0 + F16 projector | 37.802GB | 2.198GB — unsafe | 10.198GB | 42.198GB |
| Qwen3.5-35B-A3B official BF16 | 71.904GB | Does not fit files | Does not fit files | 8.096GB — bounded |
| Qwen3.5-122B-A10B Q4_K_M + projector | 77.446GB | Does not fit files | Does not fit files | 2.554GB — unsafe |
| Qwen3.5-122B-A10B official GPTQ-Int4 | 78.864GB | Does not fit files | Does not fit files | 1.136GB — unsafe |
| Qwen3.5-122B FP8 / Q8 + projector / BF16 | 127.163 / 130.781 / 250.173GB | Does not fit files | Does not fit files | Does not fit files |
L40S holds the listed 35B Q8-plus-projector files with 10.198GB nominal room, while A100 40GB leaves only 2.198GB. A100 80GB changes the listed 35B BF16 file-fit result, but its two 122B 4-bit remainders are unsafe. None of those facts determines speed: hold the artifact, runtime, context, concurrency, placement and timing definition constant.
Cooling and exact form factor are purchase gates
- Every PCIe card here is passive. The host must provide documented directed airflow. Physical fit in an open tower is not a cooling plan.
- A100 SXM is not PCIe. A bare module requires its matching baseboard, cooling, power delivery, firmware and management stack.
- L40S identity: distinguish it from L40 and A40. DisplayPort connectors do not turn a passive L40S into an actively cooled workstation card.
- MIG: A100 may be partitioned; record the MIG profile and memory visible to the process. L40S does not support MIG.
- Multi-GPU: L40S has no NVLink. A100 interconnect depends on variant/platform. Neither gives arbitrary applications one transparent pooled-memory device.
Which should you buy?
- Choose L40S when a measured workload fits 48GB and the server benefits from Ada inference/media/vGPU capabilities or display connectivity.
- Choose A100 40GB only when the workload fits below its smaller capacity with real runtime headroom and benefits from A100’s compute/MIG/interconnect environment.
- Choose A100 80GB when crossing 48GB prevents offload or partitioning and the exact passive-PCIe or SXM platform is already justified.
- Benchmark the complete systems when speed, concurrency, power or total cost decides. Hardware ceilings do not replace controlled measurements.
Create the missing controlled pair
The current fixed database has no accepted L40S or A100 observations. Build a submission record that identifies the exact board/system, exposed capacity, airflow, MIG/interconnect, driver/CUDA, artifact, runtime, context, concurrency, timing definition and peak memory. Nothing is saved or submitted automatically.
Used-market checklist
- Verify the label and part number: L40S, A100 PCIe 40GB, A100 PCIe 80GB or A100 SXM.
- Request current device identity, exposed memory, error/health evidence and any MIG state.
- Document the complete host, directed airflow, power path, PCIe lanes or SXM platform—not only the accelerator.
- Check driver/runtime support, vGPU licensing where relevant, firmware and return terms.
- Compare delivered system cost and support. Use the screened-offers directory and used-hardware checklist.
Continue: read the L40S platform guide, A100 40GB vs 80GB guide, 48GB vs 80GB capacity guide, VRAM calculator, or save private criteria and follow RSS.
Sources and limits
- NVIDIA L40S specifications
- NVIDIA A100 40GB and 80GB datasheet
- NVIDIA A100 80GB PCIe product brief
- NVIDIA CUDA compute-capability list
- Qwen3.5-35B file provenance and Qwen3.5-122B file provenance
Reviewed October 25, 2026. Specifications are sourced from NVIDIA. HighVRAM has not independently benchmarked an L40S–A100 pair. Artifact totals are sourced on the linked model guides. Used configurations and prices change.
Need the older 48GB Ampere server path? Compare A40 with A100 40GB/80GB using the same exact Qwen3.5 boundaries and platform safeguards.
For the compact-system side of the A100 decision, read DGX Spark vs A100, including exact 40GB/80GB/128GB capacity gates.