Can I run Mellum2.1-12B-A2.5B-Thinking on an RTX 6000 Ada?

Yes

Its published weights (24.3 GB) fit in the 43.2 GB an RTX 6000 Ada can use, with room for ≈ 128K tokens of context.

hf download JetBrains/Mellum2.1-12B-A2.5B-Thinking

Files and context on RTX 6000 Ada

Each file of Mellum2.1-12B-A2.5B-Thinking (and of GGUF versions the site has analyzed), and how much context fits next to it, with the context cache in 16-bit or 8-bit.

Mellum2.1-12B-A2.5B-Thinking on other hardware

Popular models that run on RTX 6000 Ada

Assumes 90% of the card's memory is usable and at least 4K tokens of context for one conversation, with the context cache in 16-bit unless noted. Fits leaves at least 20% of that memory for context; Tight leaves less.