VLLM

The sequential nature of autoregressive language models creates a fundamental bottleneck: generating each token requires a full forward pass through billions of parameters. A 70B parameter model processing a single token must load roughly 140GB of weights from memory (FP16), and memory bandwidth—not compute—becomes the limiting factor. This is why a 70B model might generate only 20-30 tokens per second on an H100, despite the GPU being capable of orders of magnitude more computation. ...

In March 2024, a team of researchers attempted to deploy a 70-billion parameter language model on a single NVIDIA H100 GPU with 80GB of VRAM. The model weights alone consumed approximately 140GB in FP16—already exceeding their hardware capacity. But even after applying 4-bit quantization to squeeze the weights down to ~40GB, the system still ran out of memory when processing contexts beyond 8,000 tokens. The culprit wasn’t the model size. It was something far more insidious: the KV cache. ...