DPC latency is a Windows system-level bottleneck that causes audio clicks, pops, and dropouts—even if your audio interface and DAW settings look perfect. It’s the time your CPU spends handling deferred procedure calls (interrupt processing) at the kernel level, and when it gets too high, your audio buffer underruns before playback can complete.
If you’ve ever experienced random audio glitches that disappear after a reboot, or clicks that appear only under certain USB or wireless conditions, DPC latency is likely the culprit. It’s invisible in your DAW and won’t show up in buffer size settings. You need a separate tool to diagnose it.
What Is DPC Latency and Why It Matters
DPC stands for Deferred Procedure Call—a Windows kernel mechanism that handles hardware interrupts and priority tasks without pausing the main CPU thread. Think of it as a interrupt queue: when your USB audio interface, mouse, network adapter, or other device needs attention, it gets added to that queue. If the queue backs up, the kernel spends more time processing these calls, and that time is stolen from your audio thread.
Audio is timing-critical. Your DAW’s audio engine assumes a predictable amount of CPU time per buffer cycle. When DPC latency spikes above 300–500 microseconds (μs) consistently, your audio thread misses its deadline. The buffer underruns, and you hear a click or pop.
The key thing: DPC latency is not the same as your audio interface’s latency or your DAW’s buffer latency. Those are known values you can measure and compensate for. DPC latency is unpredictable and system-wide. You can’t see it in your DAW settings, and it affects all audio apps equally.
How DPC Latency Differs From Audio Latency
Your audio latency is the round-trip delay from input to output—measured in milliseconds. You can set it in your DAW: 128 samples at 48 kHz equals about 2.67 ms. That’s a known, controllable number.
DPC latency is measured in microseconds (1000 microseconds = 1 millisecond) and is invisible to your DAW. It’s a Windows kernel-level metric that describes how much time the operating system spends servicing hardware interrupts instead of letting your audio app run uninterrupted.
When DPC latency is low (below 100 μs), your audio thread gets the CPU time it needs on schedule. Your buffer fills and empties predictably. When DPC latency is high and bursty, your audio thread gets delayed, the buffer underruns, and you hear artifacts.
What Causes High DPC Latency?
Several common culprits introduce DPC latency spikes:
USB devices are the most frequent offender. USB controllers, audio interfaces, and external hard drives all generate interrupts. If the driver is poorly written or the USB port is overloaded (too many devices on one hub), DPC latency rises.
Wireless devices—mice, keyboards, headsets—create frequent interrupts. Wireless reception isn’t guaranteed, so the adapter polls constantly and queues interrupts when packets arrive. Bluetooth devices can be especially problematic if your system’s Bluetooth adapter has outdated or resource-heavy drivers.
Network adapters and WiFi cards also contribute. If you’re streaming while recording, network interrupts can add to the queue.
Chipset and audio driver quality matters enormously. Cheap onboard audio drivers or outdated chipset drivers often queue interrupts inefficiently. Some manufacturers prioritize throughput over latency.
Power management and CPU throttling can mask the problem—when your CPU scales down to save power, it has less headroom to service interrupts, and DPC latency spikes.
How to Check Your DPC Latency
On Windows, you need a dedicated tool. Check your DPC latency using the DPC Latency Checker tool—it runs in real-time and shows you histogram data of your DPC latency over time.
Run the checker for at least 30 seconds without triggering audio work. Then, open your DAW, start a recording, move your mouse around, and run a stream or download in the background. The histogram will spike when high-latency events occur. You’re looking at the rightmost bar—the peak latency.
Anything under 100 μs is excellent. 100–300 μs is acceptable for most work. Above 500 μs, you’re likely to hear clicks in professional audio work, especially at low buffer sizes (64 samples or lower).
LatencyMon is another popular option that logs detailed driver information and ranks devices by their interrupt activity. It’s more verbose than DPC Latency Checker, but it helps you identify which driver is causing problems.
How to Fix High DPC Latency
Once you’ve identified the problem, fixes depend on the cause.
Start with driver updates. Uninstall your audio interface driver completely (use Device Manager, check “Delete the driver software” box), reboot, and reinstall the latest driver from the manufacturer. Outdated USB or chipset drivers are often the culprit—check your motherboard manufacturer’s support page for chipset updates.
Disconnect unnecessary USB devices. Unplug external hard drives, hubs, printers, and wireless receivers when you’re recording. Fewer devices means fewer interrupt sources. If you use a USB audio interface, try different USB ports on your motherboard—front-panel USB hubs often have worse DPC latency than rear panel ports connected directly to the chipset.
Disable Bluetooth when recording if you’re not using it. Bluetooth scanning, even when idle, generates interrupts. Turn it off in Device Manager or Settings.
If you’re using wireless peripherals, consider switching to wired alternatives during recording sessions. A wired mouse and keyboard eliminate constant interrupt polling.
Disable WiFi adapter power saving. In Device Manager, right-click your network adapter, select Properties, go to Power Management, and uncheck “Allow the computer to turn off this device to save power.” This prevents the adapter from idling and then waking up with interrupt bursts.
Check System > Device Manager for devices with warning symbols (yellow exclamation marks). These are problematic drivers that need updating or reinstalling.
If you’re still seeing spikes above 500 μs, consider whether your motherboard’s BIOS needs an update. BIOS revisions often improve USB and chipset interrupt handling.
Frequently Asked Questions
Is DPC latency the same as buffer latency?
No. Buffer latency (measured in milliseconds) is your audio interface and DAW settings. DPC latency (microseconds) is how long Windows spends handling interrupts. High DPC latency can cause audio dropouts even if your buffer size is generous.
Can I fix DPC latency on macOS or Linux?
macOS and Linux don’t use the same interrupt model as Windows. They don’t have a DPC latency metric. If you’re on those platforms, focus on audio interface latency and buffer configuration instead.
What DPC latency should I target?
Aim for consistent peaks under 300 μs for music production, under 500 μs for casual use. If your peak is 1000+ μs, troubleshoot immediately—you’ll hear clicks in your DAW.
Do gaming PCs have higher DPC latency?
Gaming PCs often have more USB devices (headsets, controllers, RGB hubs) and wireless peripherals, which increases interrupt activity. Dedicated audio PCs with minimal peripherals typically have lower DPC latency.
Dalton is an audio testing and latency optimization writer at SoundLatencyTest. He focuses on audio latency analysis, sound delay testing, recording performance, and audio troubleshooting tools for producers, gamers, streamers, musicians, and audio engineers.