The most complete results in the weights.zip line. Keep Llama's KV cache bit for bit exact at 1.6× the capacity, or choose 4-bit, 3.5-bit or 3-bit formats that serve 2.2 to 2.7× as many 128k-context users per GPU as fp8. Measured on NVIDIA H100 and H200.
Concurrent 128k-token sessions that fit after the model weights and activations. Bars are drawn to scale.
The KV budget is 92% of GPU memory less the bf16 weights and 4 GB of activations per GPU: 58.6 GB for the 8B on one H100, 416 GB for the 70B on an 8x H100 node.
| Format | Capacity vs fp8 | Output | Best for |
|---|---|---|---|
| Lossless | 1.6× vs bf16 | identical, bit for bit | cache tiers where answers must not change |
| 4-bit | 2.2× | about half of int4's error on the 8B, level with int4 on the 70B | quality-first long-context serving |
| 3.5-bit | 2.5× | int4-level text quality and retrieval on the 8B | providers already running int4-class caches |
| 3-bit | 2.7× | int4-level retrieval on the 8B | agents, document retrieval, code assistants |
Capacity for the 8B on one H100. Full details are on the KV Cache, FP8 and 3-bit pages.
| Model | Capacity gain | Restore 128k from CPU memory | Recompute the prompt |
|---|---|---|---|
| Llama-3.1-8B | 1.58× | 0.31 s | 18.8 s |
| Llama-3.1-70B | 1.59× | 0.74 s | 248.6 s |
Measured at 8k, 32k and 128k tokens, with every restored tensor checked against the original. Recompute is a full prefill with Hugging Face Transformers on the same H200.
Decode attention speed vs fp8 · NVIDIA H100, batch 8 to 64| Format | Llama-3.1-8B | Llama-3.1-70B, 128k |
|---|---|---|
| weights.zip 4-bit | 1.31 to 1.54× | 1.38 to 1.55× |
| weights.zip 3.5-bit | 1.57 to 1.89× | 1.62 to 1.84× |
Against NVIDIA's TensorRT-LLM XQA kernel for fp8. On the 8B, the 3.5-bit format matches a fully tuned int4 kernel on decode speed. On multi-key retrieval it sits slightly below int4, within measurement noise.
Quality and retrieval at 128k| Measure | int4 | weights.zip |
|---|---|---|
| 8B error, 4-bit | 1× | 0.55× |
| 8B words changed, 4-bit | 8.6% | 6.3% |
| 8B multi-key retrieval, 64k to 128k pooled, 3.5-bit (H100) | 90.9% | 89.4% |
| 8B multi-key retrieval at 128k, 3.5-bit (H100) | 81.8% | 77.3% |
| 70B error on held-out text, 4-bit | 1× | 0.91 to 0.97× |
Error is average KL divergence of next-token predictions against the uncompressed bf16 model, scored at every position of held-out 131,072-token windows. Retrieval results were independently re-analysed from the raw outputs.
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