Why System Interrupts Uses High CPU on Windows

System Interrupts is not a program. It is a Task Manager row showing the CPU time spent answering hardware, which means the driver code that responds when a device needs attention. A low number is normal, and an idle laptop measured for this page read under 1 percent. When it holds several percent or more on a quiet PC, a driver or a device is usually at fault, so the fix is to find that one. You cannot end this row, and nothing on disk is called System Interrupts.

What the number means

Devices interrupt the processor when they need something: a network card has a packet, or an audio device needs its next buffer. Windows runs the driver's interrupt routine at once, and Microsoft's driver documentation says these routines must execute as quickly as possible, so they hand the rest of the work to a deferred procedure call, or DPC, which runs shortly after at a lower priority than the interrupt but ahead of ordinary programs. System Interrupts adds up that time.

That is why it hurts more than its number suggests. While a DPC or interrupt routine runs on a core, normal threads there wait, so a slow driver shows up as audio crackle, mouse stutter or dropped frames.

Measure it, since Task Manager rounds and samples only once a second:

(Get-Counter '\Processor(_Total)\% DPC Time', '\Processor(_Total)\% Interrupt Time' -SampleInterval 2 -MaxSamples 5).CounterSamples | ForEach-Object { '{0} {1:N2}' -f $_.Path, $_.CookedValue }

Each of those read 0.38 on an idle ThinkPad with Windows 11 when this page was checked. There is no official limit, but as a rough guide, a sustained reading above 5 percent for either one on a quiet PC is worth chasing.

Find the driver

Start with what changed, then remove devices, then measure.

1. Unplug everything that is not needed: USB hubs, webcams, audio interfaces, docks, printers. Watch the number for a minute after each one. A failing USB device is a classic cause, and this step costs nothing.
2. Think about what changed: a driver or Windows update just before this began? In Device Manager, open the device's Properties › Driver and try Roll Back Driver.
3. Disable suspects one at a time in Device Manager: Wi-Fi and Bluetooth adapters first, then audio, then anything else that is not your display or disk. Watch for a minute, then enable it again.
4. Measure with LatencyMon if you still have no answer. This free tool from Resplendence reports DPC and ISR times per driver. Run it for several minutes while the problem happens, and read the Drivers tab sorted by highest execution. The file named there, such as ndis.sys for networking or a vendor's audio driver, tells you where to look.
5. Record a trace when you need more detail. Microsoft's Windows Performance Recorder is included in Windows, and it needs an admin terminal:

wpr -start CPU
wpr -stop interrupts.etl

Stop it after a minute of the symptom, then open the file in Windows Performance Analyzer and look at the DPC/ISR graphs.

What the driver name usually means

Use the PC maker's support page first on a laptop, since its drivers are built for that hardware. If the number stays high with everything unplugged, on current drivers and with a clean restart, hardware is a real possibility, especially after a drop or spill. A Linux live USB can help here: if the machine still stutters there, Windows drivers are less likely to be the cause.

What not to do

• Do not look for a way to end it. There is no process behind this row, so Task Manager has nothing to stop.
• Do not install a driver update utility. They often pick the wrong build for a laptop, and that can be the problem you are trying to fix.
• Do not change interrupt or MSI settings in the registry from a forum post. A wrong value can stop the PC from booting.
• Do not pay for a "system optimizer". Nothing in it can fix a driver bug, and it adds its own background work.

Where Mole fits

Mole for Windows does not list System Interrupts, because its Status page reads real processes and this row is not one. It has no driver tools either. It is useful for ruling the other side out: if Status shows a process actually working hard, the problem may be that process, so read high CPU usage on Windows first. If no process explains the load, the steps above are the right path. For the other Task Manager rows that are not ordinary programs, see System Idle Process.

FAQ

What is System Interrupts in Task Manager?

It is the time the CPU spends running driver code that responds to hardware, shown as a single row. It has no file, and no program sits behind it.

How much CPU should System Interrupts use?

Usually well under 1 percent at idle, and it can rise briefly under heavy network or disk work. Several percent held on a quiet PC is worth investigating.

Can I disable System Interrupts?

No. It is not a service or a program. It reports work that hardware needs done, so the fix is the driver or the device causing it.

Is System Interrupts a virus?

No. Malware can run its own driver, though that is rare, and a scan with Microsoft Defender is reasonable if LatencyMon names a driver you do not recognize.

Why does System Interrupts make my audio crackle?

That code runs ahead of ordinary programs, so a slow driver delays the audio program on that core past its next buffer. LatencyMon was built for this case and names the driver.