Can I run it?

Can I run Qwythos 9B Claude Mythos 5 1M on GeForce RTX 5080?

Runs

Runs fully on your GeForce RTX 5080 at Q8_0, 8K context, about 54–73 tok/s. Weights 8.87 GB plus 0.27 GB of KV cache — 9.54 GB of 14.7 GB usable. Up to 128K context still fits.

Best quantQ8_0

Working context8K

Max that fits128K

Speed54–73 tok/s

Weights8.87 GB

KV cache0.27 GB

Total9.54 GB

Usable14.7 GB

Qwythos 9B Claude Mythos 5 1M details · GeForce RTX 5080 page · How this estimate is made

Run commands

llama.cpp

llama-server -hf empero-ai/Qwythos-9B-Claude-Mythos-5-1M-GGUF:Q8_0 -c 8192 -ngl 32

No matching name in the Ollama library snapshot.

LM Studio

lms get empero-ai/Qwythos-9B-Claude-Mythos-5-1M-GGUF
# Then load quant Q8_0

Assumptions

Estimate, not a benchmark. Decode speed uses a memory-bandwidth model at 55–75% of peak.
KV cache is FP16. Engine overhead assumes llama.cpp (0.3 GB + 1% of the weights). Ollama is closer to 0.9 GB + 3%, LM Studio closer to 1 GB + 3%.
Q8_0 size is the real GGUF file size from Hugging Face.
0.5 GB is reserved because this GPU also drives a display, then 5% of the rest is left free.
Speed is quoted at 8K context, not at the maximum context that still fits.

Larger models that also fit

Can I run Qwen3.8 27B on GeForce RTX 5080? — Tight fit, UD-IQ4_XS, 36–49 tok/s
Can I run gemma 4 12b it on GeForce RTX 5080? — Tight fit, UD-Q8_K_XL, 31–43 tok/s
Can I run Qwen3.5 9B on GeForce RTX 5080? — Tight fit, UD-Q8_K_XL, 40–54 tok/s

Updated 2026-10-24. Profile on this page is the device default plus 32 GB of DDR5-5600 system RAM.