Can I run Ornith-1.5-35B-A3B-GGUF on an RTX 4090?
No
Even its smallest file (Q4_K_M, 21.7 GB) is more than an RTX 4090 can hold (21.6 GB usable): it needs 2 of them.
Files and context on RTX 4090
Each file of Ornith-1.5-35B-A3B-GGUF (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.