Why Does System Idle Process Use 98% of the CPU?

High Percentage

System Idle readings will be higher the fewer the processes that are engaging the system and the less intensive these processes are. Thus, readings of 95 to 98 percent for System Idle are quite normal and don't signify that your PC is literally running out of processing capacity for the tasks at hand. Most tasks managed by the CPU will each occupy substantially less than 1 percent of the processor use and will therefore be assigned 00 percent in the Task Manager window.

Windows OS is designed in a way that requires one or more CPU processes to be running at all times. The ongoing System Idle process isn't in fact an actionable process but rather a counter of the CPU's idle bandwidth, ready and available to be dispensed onto other tasks. But this perpetuity of this process is vital to the continuous functioning of your PC as it ensures that the system never comes to a standstill, even if no actual program is running on it and therefore no active processes are engaging the CPU.

System Idle also allows power-saving mechanisms to be triggered when it's detected as the sole process running on the CPU. The exact power-saving mechanisms and schedules differ across various Windows operating systems, but they can include reducing screen brightness or reducing processor power consumption.

System slowdowns are in no way related to or caused by high System Idle readings. In fact, a high system idle reading suggests just the opposite -- your CPU has plenty of available processing power available for use. Other bottlenecks in your system may include your RAM and hard disk usage, so troubleshooting these components is your next step.