The occlusion culling option reduces the impact of CPU limited scenario's by no longer drawing objects that are masked and offscreen. Generally this reduces cpu usage (or just improves the rate in which visible data reaches the gpu) which increases the GPU usage and the framerate as a result.

What you are seeing is a result of the culled data no longer being in video memory, and having to be streamed back in from system memory - which you have little of on that 930 so its actually fishing the data from the GPU Commit (Paged out) memory.


Windows Memory Management is actually fairly complicated, so you cannot rely on the memory used column in task manager.