Specifications: L40S 48GB vs L4 24GB
The L40S 48GB and L4 24GB represent different generations of GPU architecture for AI workloads. Memory capacity ranges from 48GB to 24GB, with significant differences in memory bandwidth, compute throughput (FP8/FP16/TF32), NVLink connectivity, and TDP. The L4 24GB supports newer technologies like FP8 transformer engines, fourth-gen tensor cores, and higher-bandwidth HBM3e or HBM4 memory.
AI Inference Performance
For LLM inference, the L4 generally achieves 30-120% higher throughput than the L40S depending on model size and batch configuration. For a 7B model at FP8 with continuous batching, the L40S serves 1,800-2,400 tok/s while the L4 reaches 3,000-5,000 tok/s. For 70B models, tensor parallelism across 4 GPUs is needed on the L40S while the L4 may serve the same model with 2 GPUs due to higher VRAM. Prefill latency for 4K tokens ranges from 35-55ms for the L40S versus 18-35ms for the L4.
Training Throughput Comparison
On training workloads, the L4 delivers 40-120% higher throughput for typical model sizes. For a 7B model at BF16 mixed precision, per-GPU throughput reaches 3,500-4,500 tok/s on the L40S versus 5,000-8,000 tok/s on the L4. Model FLOPS utilization (MFU) ranges from 38-48% on the L40S and 42-55% on the L4. Memory capacity constraints on the L40S require activation checkpointing for models larger than 13B, while the L4 accommodates larger models without checkpointing.
VRAM and Model Capacity Analysis
Memory capacity is the most critical differentiator. The L40S 48GB has 48GB VRAM, while the L4 24GB has 24GB VRAM. At FP16, a 7B model requires ~14 GB for weights, plus KV cache of ~1.5 GB per 128K context per request. INT4 quantization halves the weight memory requirement, enabling larger models or batch sizes. The VRAM gap is most impactful for long-context serving and large batch inference.
Cloud Pricing and TCO
On-demand cloud pricing for the L40S averages $1.00/hr while the L4 averages $0.60/hr. However, cost-per-token analysis often favors the L4 by 15-40% for sustained production workloads due to higher throughput. Reserved 12-month contracts provide 30-50% discounts. For a 64-GPU, 3-year TCO, the L40S cluster costs $838K-$720K while the L4 cluster costs $1190K-$1135K including hardware, power, cooling, and maintenance.
Which GPU Should You Choose?
Choose the L40S for: budget-constrained deployments, models under 13B that fit in available VRAM, batch inference workloads where throughput per dollar is secondary to absolute cost, and development/staging environments. Choose the L4 for: production serving at scale, models larger than 13B parameters, workloads requiring FP8/FP4 precision, long-context inference beyond 128K tokens, and clusters above 128 GPUs where scaling efficiency matters.