If you are talking about external operations, like shubham said - nothing. If you are talking about internal operations, the answer is a little different. DMA comes to mind.
Nothing....
But if you have dual core or better processor, while doing simple tasks like web surfing, accessing your OS, the CPU usage generally hovers around 0-5%
If you are talking about external operations, like shubham said - nothing. If you are talking about internal operations, the answer is a little different. DMA comes to mind.