Ever since I changed to ADSL connection some month ago I have noticed one odd thing: when I am connected the CPU usage, as shown in Task Manager, jumps up and down when the machine is idle. By idle I mean, in this case, no input activity (mouse/kb), no programs running (except background programs / processes; firewall and AV), and no net activity (packages sent/received).

If I have the Task Manager's update speed set to High, the CPU History looks like added screenshot. It jumps between 7 and 13 %. If set to normal speed it is around 6 to 8 %.

I know my machine that much, that I know what processes normally are running, nothing odd around. The culprit to this CPU activity seems to be the System process, i.e. ativity shown for that process. Now that one is not easy to track further, since it contains the kernel-mode system threads, and a whole bunch is running under it.

With Sysinternals Process Explorer I can do some more research. Here the System process