Compatibility check
Can you run Llama 3.1 8B Instruct on the Radeon RX 7800 XT?
Yes, with quantization. Llama 3.1 8B Instruct does not fit the Radeon RX 7800 XT (16 GB) in FP16, but it runs at INT8 (8-bit) using about 9.7 GB (61% of VRAM). Use a GPTQ, AWQ, or GGUF build to get there, and keep prompts moderate to leave room for the KV cache.
Memory breakdown
Weights plus a 0.5 GB KV cache at 4,096tokens, against the card's 16 GB. Verdicts leave ~10% headroom for activations and fragmentation.
| Precision | Weights | KV cache | Total | % of 16 GB | Fit |
|---|---|---|---|---|---|
| FP16 / BF16full quality | 18.5 GB | 0.5 GB | 19 GB | 119% | No |
| INT8 (8-bit)near-full quality | 9.2 GB | 0.5 GB | 9.7 GB | 61% | Fits |
| INT4 (4-bit)GPTQ / AWQ / GGUF Q4 | 4.6 GB | 0.5 GB | 5.1 GB | 32% | Fits |
Planning estimates, not a substitute for profiling. Real usage varies with the inference runtime, batch size, and how much context you actually use — the KV cache grows linearly with prompt length.
GPUs that run Llama 3.1 8B Instruct
Cards where this model fits (at its best precision):
Models that fit the Radeon RX 7800 XT
Other popular models that run on this card:
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Frequently asked questions
Can the Radeon RX 7800 XT run Llama 3.1 8B Instruct?
Not in FP16, but yes at INT8 (8-bit), where it uses about 9.7 GB versus the card's 16 GB.
How much VRAM does Llama 3.1 8B Instruct need?
Approximately 18.5 GB in FP16, 9.2 GB in INT8, and 4.6 GB in 4-bit for the weights, plus a KV cache of about 0.5 GB at 4,096 tokens.
Does quantization let Llama 3.1 8B Instruct fit on the Radeon RX 7800 XT?
Yes. Dropping to INT8 (8-bit) brings total usage to about 9.7 GB, which fits the 16 GB card with headroom for the KV cache.
What happens to memory with longer context?
The KV cache grows linearly with prompt length. At 4,096 tokens it is about 0.5 GB here; doubling the context roughly doubles that term, so long-context use can push a tight fit over the edge.