[tremon]

Is VRAM not directly accessible by the system then? Since it's mapped directly into the CPU's address space, I had assumed that there's a simple DMA controller managing said access and I would then also naively assume that said controller is separate (or at least on a separate power plane) from the actual GPU.

[kllrnohj]

they are talking about the scenario of having a discreet GPU in addition to the GPU on the CPU. So there's 2 GPUs, and the nvidia one has its own VRAM (typically of the GDDR variety even) that isn't shared with system RAM (hence the purpose of this project). So that also means 2 memory controllers.