The biggest open models, like DeepSeek V4 and Qwen3, are mixtures of experts. They're split into thousands of small expert networks, and each word only uses a few of them. So the whole model never has to sit in fast memory at once.
Pelica keeps the parts every word needs on the GPU, along with the experts the model reaches for most. The next tier waits in RAM. Everything else stays on your SSD and is read just in time: Pelica runs the next layer's router early to guess which experts are coming, and gets the top pick right about 99% of the time.
Experts move up as they're used and drop down when they go quiet, so the fast memory keeps working on whatever your conversation needs right now. None of this changes the model's answers. Every speedup is checked to produce exactly the same words.