What’s the real difference between RTX 4090 and A100? Price gap is 3× — how to choose

RTX 4090: ~¥1.5–2.5/hour; A100 80G: ~¥4.6–7/hour—3× difference. Where does it come from?

Four real differences

① VRAM24GB vs 80GB—the most fundamental difference: your entry ticket for large-model training/inference; InternetA100 supports NVLink, delivering massively superior multi-GPU parallel efficiency compared to RTX 4090’s PCIe; Memory Bandwidth2 TB/s vs 1 TB/s—inferencing throughput drops significantly; ④ Stability-focused positioningData center GPUs are designed for 7×24 full-load operation.

When is an RTX 4090 sufficient?

LoRA/QLoRA fine-tuning for models ≤13B, SD/Flux image generation, video generation, and inference for models ≤13B — the A100 delivers no perceptible performance gain here; renting it would simply waste money.

When Do You Absolutely Need an A100?

Full-parameter fine-tuning (7B requires ~80GB), quantized 70B inference (≥40GB), multi-GPU distributed training, 7×24 production inference.

Today’s Price Comparison

4090：

A100 80G：

One-liner:VRAM requirement sets the floor; budget sets the ceilingTry this site firstPickerCalculate VRAM requirements first, then consult the price table to decide.