What is DPC latency?
Deferred procedure calls (DPCs) are how Windows prioritises important processes that may be running simultaneously. If non-audio processes demand too much processing time, this disrupts the timing of audio driver data, leading to glitchy audio, or even device disconnections.
A common cause of DPC latency is out-of-date device drivers and poorly optimised processes. Streaming audio involves many processes and drivers, while many others can interrupt this audio stream.
DPC latency can be unavoidable with some combinations of components and drivers, so drivers have some built-in resilience. Therefore, we recommend you only continue with DPC latency tests if there are audible glitches or dropouts in the audio stream after completing all of the steps in both of the following articles:
Troubleshooting glitchy audio on Windows
Analysing DPC latency
To analyse whether DPC latency could be causing glitchy audio on your system, you can run the following software tool: LatencyMon.
In LatencyMon, click the ▶ Play button and then play audio from any application through your audio interface for at least fifteen minutes, with the glitches occurring at least once. If there aren't any DPC problems, you will see the following:
Conclusion: Your system appears to be suitable for handling real-time audio and other tweaks without dropouts.
If there are problems, you will see a message similar to the following instead:
Conclusion: Your system appears to be having trouble handling real-time audio and other tasks…
You can find the process or driver causing the highest DPC latency here:
Highest reported DPC routine execution time (µs) :
To see all the drivers and processes that are causing high DPC latency, navigate to the Drivers tab in LatencyMon, and click Highest execution (ms) twice to sort the drivers so those causing the highest DPC latency are at the top — any drivers exceeding 0.500000ms could be causing issues with audio.
Troubleshooting DPC latency
If you aren't confident making changes to your PC's components, contact the manufacturer or a PC technician for assistance.
General DPC troubleshooting
Before looking into any specific drivers or processors that may be causing the DPC latency, you should first complete some general troubleshooting if you have not already done so. The LatencyMon website includes some initial troubleshooting advice that is worth running through in addition to the steps below: Using LatencyMon.
1. Windows updates
Many updates for system processes and drivers are delivered via Windows Update, so you should first make sure Windows is up-to-date: Install Windows Updates - Microsoft Support.
2. Intel and AMD updates
If you are using an Intel system, you can use the Driver Update Support Assistant to find driver updates for your system. It can be downloaded here: Intel® Driver & Support Assistant.
If you are using an AMD system, you can use the AMD Auto-detect and Install tool to find driver updates for your system. It can be downloaded here: Drivers and Support for Processors and Graphics.
For ARM systems, check with the manufacturer of your PC or its components.
3. Other updates
To ensure all your other drivers and your BIOS are up-to-date, follow the steps here if you have not already done so: Update drivers and BIOS and Update in Device Manager.
4. Disable audio devices and disconnect peripherals
Disable unused audio devices, like your PC's built in soundcard, to ensure unused audio drivers are not conflicting with your Focusrite drivers. Here's how to disable them:
- Right-click
Start and open Device Manager.
- Click the > arrow to expand Sound, video and game controllers.
- Right-click on any non-Focusrite devices and select Disable device.
Additionally, to determine if any other hardware devices or their drivers are causing the DPC latency on your system, simply disconnect any and all devices that you can. Should you find that this resolves the glitchy audio, reconnect the devices one at a time to see if you can identify the culprit. If you do, update its drivers, reconnect it to a different port on your PC, check with the manufacturer for troubleshooting steps, or try an alternative device if possible.
Targeted DPC troubleshooting
If you aren't confident making changes to your PC's components, contact the manufacturer or a PC technician for assistance.
There are a number of common processes that may appear in the LatencyMon results. Once you've identified which ones are causing high DPC latency, follow the specific steps we've put together for those processes below:
ACPI.sys
This is a power management driver. Ensure you have created the custom power plan and checked the settings described here: Custom power plan and USB power management settings. If you are using a laptop, try connecting the power supply rather than running on battery.
You should also ensure that your drivers and BIOS are up-to-date if you have not already done so: Update drivers and BIOS.
If these steps do not resolve the issue, please continue to Further troubleshooting below.
amdkmdag.sys
This is an AMD GPU driver. Follow the general and AMD steps for dxgkrnl.sys below.
dxgkrnl.sys
This is a graphics driver. Ensure your GPU drivers are up-to-date, try an optimised version of the driver if one is available, and test using integrated graphics instead if your PC has this feature. You should also check with your GPU and motherboard manufacturer to confirm which PCIe slot the GPU should be installed in, and to confirm any other installation and setup requirements.
AMD GPU
You can update your AMD GPU drivers with AMD Software: Adrenaline Edition.
If the Adrenaline Edition driver is already up-to-date or updating does not resolve the issue, try installing AMD Software: PRO Edition if possible with your GPU. This is optimised for stability in professional applications, like audio and video production.
NVIDIA GPU
You can update your NVIDIA GPU drivers with the NVIDIA App or download the latest drivers from their website: Download The Official NVIDIA Drivers | NVIDIA.
If the Game Ready driver is already up-to-date or updating does not resolve the issue, try installing the Studio driver from NVIDIA's website instead. This is optimised for stability in professional applications, like audio and video production.
Test integrated graphics
To confirm if your GPU is the only cause of the glitching, you can test with integrated graphics if your PC has integrated graphics separate from your GPU.
Switch to integrated graphics
- Check that there is a display connector on your PC that is not part of your GPU.
- Connect your display screen to this port to see if it is functioning while your GPU is still enabled — if not, reconnect it to your GPU.
- Right-click
- Click the > arrow to expand Display adapters — you should see at least two display adapters if integrated graphics are functioning.
- Right-click each device and select Enable device to ensure your integrated graphics are enabled.
- Right-click your GPU in Display adapters and select Disable device.
- Connect your display screen to the integrated graphics display connector on your PC if you haven't already done so.
You can then complete any necessary tests to see if disabling your GPU has had any effect.
Should you find that the issue is still unresolved, you can try moving the GPU to a different PCIe slot if possible. It is also worth reaching out to the GPU manufacturer for further assistance as well.
If you aren't confident making changes to your PC's components, contact the manufacturer or a PC technician for assistance.
If these steps do not resolve the issue, please continue to Further troubleshooting below.
ndis.sys
Network Driver Interface Specification is a critical networking component of Windows. It handles networked computers, as well as any connected devices or hardware. Latency or corruption involving ndis.sys can result in audio artefacts, decreased system performance, and even blue or black screens.
Any applications that may be connecting to the internet could cause high network driver DPC latency, so you should first close all applications that may be connecting to the internet to see if this alleviates the glitching. Check Task Manager (Ctrl + ⇧ Shift + Esc) as some web applications and browsers may be running in the background, even if you don't have any windows open.
Next, you should ensure all network adapters are up-to-date in Device Manager:
- Right-click
- Click the > arrow to expand Network adapters.
- Right-click each device and click Update driver where available.
- Select Search automatically for drivers and install any drivers that Windows recommends.
Also, it is worth following the steps in this article regarding antivirus software if you haven't already done so: Third-party antivirus and anti-malware. Additionally, try disabling and then temporarily uninstalling any VPN software.
If you are using Wi-Fi, disable the Wi-Fi in Advance network settings and try a wired connection, and if you are using a wired connection, disable the ethernet network card and try switching to Wi-Fi. Also, go to your Bluetooth settings and disable Bluetooth.
Finally, try disabling all network adapters as per the instructions in this article: Disable network cards.
Should you find that the steps above do resolve the issue, you may need to permanently switch to whichever network adapter or Bluetooth configuration worked. You can also try moving the network, Wi-Fi, or Bluetooth card to a different PCIe slot on your motherboard.
If you aren't confident making changes to your PC's components, contact the manufacturer or a PC technician for assistance.
If these steps do not resolve the issue, please try the steps for tcpip.sys if you haven't already, and then continue to Further troubleshooting below.
nvlddmkm.sys
This is an NVIDIA GPU driver. Follow the general and NVIDIA steps for dxgkrnl.sys above.
storport.sys
This is a Microsoft storage port driver related to your PC's storage drives. It can also cause high DPC latency if the standard controller for these drives is not being used. Reverting to the standard controller can fix the high DPC latency.
Switch to Standard SATA AHCI Controller
- Right-click
- Click the > arrow to expand IDE ATA/ATAPI controllers — you should see the Standard SATA AHCI Controller and at least one other device.
- Right-click the other device and go to Properties → Driver → Update Driver…
- In the window that opens, select Browse my computer for driver software, then Let me pick from a list of device drivers on my computer.
- Choose Standard SATA AHCI Controller and click Next.
Once the installation completes, your PC should be using the Standard SATA AHCI Controller. You can test to see if this has resolved the issue or not.
System restore processes and other applications that are creating backups may contribute to high DPC latency in this case. Disable any software that may be contributing to this, and try a clean boot if you haven't already done so: Troubleshooting with a ‘clean boot’.
DPC latency caused by storport.sys can sometimes also be resolved by the System File Checker, Deployment Image Servicing and Management, and Check Disk:
Run System File Checker
To scan and repair any issues with the Windows system image, you can run System File Checker:
- Click
- Right-click Command Prompt and select Run as administrator.
- Type the following command into Command Prompt:
sfc /scannow
- Press ↵ Enter — do not close the Command Prompt window until the verification is 100% complete.
Check the scan results and, if any files have been repaired, test to see if the issue has been resolved.
Run Deployment Image Servicing and Management (DISM)
Deployment Image Servicing and Management will modify and repair system images if there are any corruptions:
- Click
- Right-click Command Prompt and select Run as administrator.
- Type the following command into Command Prompt:
DISM /Online /Cleanup-Image /RestoreHealth
- Press ↵ Enter — do not close the Command Prompt window until the process is 100% complete. If the command appears stuck, this is normal. The process can take some time to complete.
After this completes, test to see if the issue persists.
Run Check Disk (chkdsk)
This will repair any disk errors. Check Disk can be run on HDD, SSD, and NVMe storage safely.
- Click
- Right-click Command Prompt and select Run as administrator.
- Type the following command into Command Prompt:
chkdsk C: /R
- Press ↵ Enter.
- When prompted, confirm that you want to carry out the disk repair the next time the system restarts by entering Y.
- Restart your PC.
After the restart, check to see your the issues have been resolved at all.
If these steps do not resolve the issue, please complete the rest of Further troubleshooting below.
ohci1394.sys
This is a critical Windows component on systems with FireWire cards or devices. Microsoft has discontinued support for FireWire, and the final version of Windows we support Saffire FireWire with is Windows 10 version 1809 build 17763.
You will need to download and install or reinstall the Windows Legacy FireWire driver, but ensure you do not update past our last supported version of Windows 10. Here are some additional steps to try:
- Unplug all FireWire devices and check if the DPC issues persist.
- Try a different FireWire port.
- If you have built-in FireWire ports, try a PCI or PCIe FireWire card instead and vice versa.
- Update the drivers for your FireWire devices.
If these steps do not resolve the issue, please continue to Further troubleshooting below.
tcpip.sys
Transmission Control Protocol/Internet Protocol, or TCP/IP.sys, handles communication between computers. If TCP/IP.sys becomes corrupt, it will often result in stuttering audio and blue or black screens.
To resolve this, try these steps in Command Prompt:
Command Prompt steps
- Click
- Right-click Command Prompt and select Run as administrator.
- Type
netsh winsock reset, then press ↵ Enter. - Type
netsh int ip reset, then press ↵ Enter. - Type
ipconfig /release, then press ↵ Enter. - Type
ipconfig /renew, then press ↵ Enter. - Type
ipconfig /flushdns, then press ↵ Enter. - Reboot your computer.
If these steps do not resolve the issue, please try the steps for ndis.sys if you haven't already, and then continue to Further troubleshooting below.
USBPORT.sys
This is a USB chipset driver. Firstly, you should ensure that your drivers and BIOS are up-to-date if you have not already done so: Update drivers and BIOS.
Additionally, double-check you have completed the following USB optimisations:
Built-in SD card readers have also been seen to cause high USBPORT.sys DPC latency. Open Device Manager and try disabling any SD, MMC, or Compact Flash entries to see if this reduces or resolves the glitches.
If these steps do not resolve the issue, please continue to Further troubleshooting below.
Wdf01000.sys
This is a system file that is part of the Windows Driver Framework. High DPC latency from Wdf01000.sys can be related to corrupt system files, or issues with other drivers.
Corruptions may be resolved by running System File Checker, Deployment Image Servicing and Management, and Check Disk:
Run System File Checker
To scan and repair any issues with the Windows system image, you can run System File Checker:
- Click
- Right-click Command Prompt and select Run as administrator.
- Type the following command into Command Prompt:
sfc /scannow
- Press ↵ Enter — do not close the Command Prompt window until the verification is 100% complete.
Check the scan results and, if any files have been repaired, test to see if the issue has been resolved.
Run Deployment Image Servicing and Management (DISM)
Deployment Image Servicing and Management will modify and repair system images if there are any corruptions:
- Click
- Right-click Command Prompt and select Run as administrator.
- Type the following command into Command Prompt:
DISM /Online /Cleanup-Image /RestoreHealth
- Press ↵ Enter — do not close the Command Prompt window until the process is 100% complete. If the command appears stuck, this is normal. The process can take some time to complete.
After this completes, test to see if the issue persists.
Run Check Disk (chkdsk)
This will repair any disk errors. Check Disk can be run on HDD, SSD, and NVMe storage safely.
- Click
- Right-click Command Prompt and select Run as administrator.
- Type the following command into Command Prompt:
chkdsk C: /R
- Press ↵ Enter.
- When prompted, confirm that you want to carry out the disk repair the next time the system restarts by entering Y.
- Restart your PC.
After the restart, check to see your the issues have been resolved at all.
If this does not resolve the issue, run through the steps for all the other processes listed above, because other drivers and processes can lead to high DPC latency from Wdf01000.sys. Repairing or reinstalling Windows may also be beneficial. Then, please complete the rest of the Further troubleshooting steps below.
Further troubleshooting
Check the BIOS
If you haven't already done so, please see Update drivers and BIOS to check your BIOS, chipset, on other components and apply any available updates.
The following steps involve advance settings in your PC's BIOS. If you aren't confident making changes to your PC's BIOS and other advanced settings, contact the manufacturer or a PC technician for assistance.
Disable ‘C-states’ in the BIOS
Also, if you haven't already done so, please complete these steps: Disable ‘C-states’ in the BIOS.
Other BIOS features
Next, you can try disabling any unnecessary devices and features in the BIOS. For example, serial or parallel ports, legacy drive features, and built-in or onboard audio. You should then consider disabling any stepping technologies like Intel SpeedStep (EIST) or AMD K8 Cool’n’Quiet — this does mean your CPU will likely run at max clock, and battery life will be impacted if you're using a laptop.
Other system checks
The following system checks can resolve issues with system files that may be contributing to DPC latency and glitchy audio. Please run the System File Checker, Deployment Image Servicing and Management, and Check Disk. If you've already done this as part of the targeted troubleshooting, move on to the next step below: Check IRQ conflicts.
Run System File Checker
To scan and repair any issues with the Windows system image, you can run System File Checker:
- Click
- Right-click Command Prompt and select Run as administrator.
- Type the following command into Command Prompt:
sfc /scannow
- Press ↵ Enter — do not close the Command Prompt window until the verification is 100% complete.
Check the scan results and, if any files have been repaired, test to see if the issue has been resolved.
Run Deployment Image Servicing and Management (DISM)
Deployment Image Servicing and Management will modify and repair system images if there are any corruptions:
- Click
- Right-click Command Prompt and select Run as administrator.
- Type the following command into Command Prompt:
DISM /Online /Cleanup-Image /RestoreHealth
- Press ↵ Enter — do not close the Command Prompt window until the process is 100% complete. If the command appears stuck, this is normal. The process can take some time to complete.
After this completes, test to see if the issue persists.
Run Check Disk (chkdsk)
This will repair any disk errors. Check Disk can be run on HDD, SSD, and NVMe storage safely.
- Click
- Right-click Command Prompt and select Run as administrator.
- Type the following command into Command Prompt:
chkdsk C: /R
- Press ↵ Enter.
- When prompted, confirm that you want to carry out the disk repair the next time the system restarts by entering Y.
- Restart your PC.
After the restart, check to see your the issues have been resolved at all.
Check IRQ conflicts
Interrupt requests (IRQs) are used for operations like mouse clicks, keystrokes, or key presses on MIDI controllers. IRQs tell the processor to stop what it’s doing and register the operation. Each operations has a channel for IRQs, but a conflict occurs when two pieces of hardware try to use the same channel.
In the past, devices could not share IRQ channels, but modern systems are able to handle this better. Therefore, IRQ conflicts alone are not indicative of an issue. However, you can check IRQ conflicts to see which specific devices might be conflicting with your Focusrite interface. Try updating the conflicting device, moving it to a different port or PCIe slot, and finally disconnecting it altogether.
Here's how to check for IRQ conflicts:
- Right-click
- Go to View → Resources by type.
- Scroll down to the (PCI) devices.
- Right-click on your Focusrite audio interface and select Properties.
- Go to the Resources tab.
- Select the IRQ and check the Conflicting device list.
Troubleshooting with a ‘clean boot’
Next, you should try troubleshooting with a series of clean boots. Before you try a clean boot, make sure you have removed any bloatware and unwanted apps as described here: Remove bloatware and unwanted apps.
A ‘clean boot’ will enable you to start your computer with a minimal set of apps, drivers, and services running. This can help you to determine if any app, driver, or service is contributing to any issues you are experiencing. You should follow the steps at the link below:
In the event that none of the steps above resolve the issues you're experiencing, we recommend you contact your computer, CPU, GPU, and motherboard manufacturers for further assistance. Alternatively, you can contact a PC technician for further troubleshooting.
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