Dell XPS Audio Dropouts - ACPI.sys Latency

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eliader

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Hi all. I'm just looking for a bit of help

After having had to replace the motherboard in my Dell XPS 15 9550 laptop, I'm experiencing an issue with high DPC latency / audio drop outs (i.e. clicks & pops) whenever audio comes out of the speakers. This is when doing very basic things such as playing a track in iTunes or watching a video on YouTube (with no other programs open)- in these instances CPU / GPU / SSD / RAM usage is very low, but the pops still occur. My job is music-related so this makes the computer pretty useless at the moment.

Using the diagnostic program LatencyMon, the high DPC latency issue seems related to the ACPI.sys driver. I didn't experience this problem before with the previous motherboard, however after some research I have discovered that many people have been experiencing the same thing with Dell XPS laptops (look up 'XPS 15 ACPI.sys'). People have even replaced their laptops and had the same issue!

There don't seem to be many definitive fixes for the problem. To try and fix the issue I have done the following:
- ensure latest audio drivers are installed
- ensure latest BIOS is installed
- disabled / enabled Realtek audio driver
- fresh installation of Windows 10 Pro (keeping files and apps)
- ensure enough SSD space is free (I have 203GB free)
- disabled Speedstep
- using ThrottleStop to ensure CPUs are running at their optimum without overheating
- making sure Intel Rapid Storage Technology is installed and running
- changed maximum processor state to 99% instead of 100% to avoid turbo boost activation

The last reply in this forum post is from a user who says they found a fix which completely solved the issue for them. It's as follows: going into Device Manager & 'disabling' the root nodes of main components such as SSD, USB controllers, HD controllers. They then say that the computer will recognize and re-enable these devices at startup... My main question is, is this a bad idea? What's the worst that could happen?

I'm really desperate to fix this DPC latency issue, but I think I've run out of things to try, and worried things might take a turn for the worse if I try this last step.

Thanks for any help you may be able to give
 
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Solution
I understand your frustration with the high DPC latency and audio dropouts on your Dell XPS 15 9550 laptop. This can be a frustrating issue, especially if your job is music-related. I'll try to provide some help and suggestions.
First, it's worth noting that the ACPI.sys driver is responsible for handling power management and device configuration on your computer. If there's an issue with this driver, it can cause high DPC latency and audio dropouts.
Regarding the suggested fix of disabling the root nodes of main components in Device Manager, it's not recommended to do so as it can potentially cause system instability or even render your computer unusable. It's best to avoid making such changes unless you are confident about the...
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I understand your frustration with the high DPC latency and audio dropouts on your Dell XPS 15 9550 laptop. This can be a frustrating issue, especially if your job is music-related. I'll try to provide some help and suggestions.
First, it's worth noting that the ACPI.sys driver is responsible for handling power management and device configuration on your computer. If there's an issue with this driver, it can cause high DPC latency and audio dropouts.
Regarding the suggested fix of disabling the root nodes of main components in Device Manager, it's not recommended to do so as it can potentially cause system instability or even render your computer unusable. It's best to avoid making such changes unless you are confident about the implications.
Now, let's explore some other possible solutions:
1. Update drivers: Ensure that all your drivers are up to date, including the ACPI.sys driver, audio drivers, and any other relevant drivers for your hardware components. Visit the Dell support website and download the latest drivers for your model.
2. Disable certain devices: You can try disabling specific devices in Device Manager temporarily to isolate the issue. For example, you can disable the Wi-Fi adapter or Bluetooth if they are not currently in use. This might help identify if any specific hardware component is causing the issue.
3. Disable power-saving settings: In the Power Options settings, make sure that power-saving options, such as CPU power-saving states or USB selective suspend, are disabled. These settings can sometimes affect DPC latency.
4. Disable audio enhancements: In the Sound settings, disable any audio enhancements, as they can sometimes interfere with the audio output and cause audio dropouts.
5. Adjust power plan settings: Try changing the power plan settings to "High Performance" and see if it makes any difference. This might help ensure that the CPU and other components are running at their maximum performance.
6. Check for background processes: Use Task Manager to check for any background processes that might be consuming significant system resources. Close unnecessary applications and processes to minimize CPU usage.
7. Run a system scan: Perform a full system scan using your preferred antivirus software to check for any potential malware or viruses that could be causing the issue.
If none of these solutions work, it might be worth contacting Dell support for further assistance. They may be able to provide more specific troubleshooting steps or advise on any known issues with your model that could be causing the problem.
I hope these suggestions help you resolve the DPC latency and audio dropout issues on your Dell XPS 15 9550 laptop.
 
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Solution
It sounds like you're dealing with the infamous DPC latency issues caused by ACPI.sys, which is unfortunately a common culprit when it comes to audio dropouts, particularly on Dell XPS laptops. This system file is related to power management and hardware communication, making it tricky to address without causing unintended system instability.
Let’s explore how to tackle this.

Why This Happens​

ACPI.sys latency spikes can result from:
  1. Power Management Conflicts:
    • Dell laptops often have aggressive power management settings that try to balance performance and battery life, but these can interfere with real-time processes (e.g., audio).
  2. Drivers Needing Updates or Reconfiguration:
    • Outdated or buggy device drivers may increase DPC latency by poorly interacting with ACPI.sys.
  3. BIOS Settings:
    • Misconfigured BIOS parameters (e.g., C-States or SpeedStep) can directly influence how ACPI.sys handles power transitions.

Steps to Fix the Issue​

While not all issues can be fully resolved (due to ACPI.sys being core to Windows), these strategies can help minimize its impact:

1. Update Key Drivers​

Outdated or poorly optimized drivers often exacerbate DPC latency.
  • Device Drivers:
    • Update directly from Dell’s support page for your XPS model (rather than relying on Windows Update or generic drivers).
    • Focus on:
      • Intel chipset drivers.
      • Intel Dynamic Platform and Thermal Framework.
      • Audio drivers (try both Dell's version and the manufacturer’s version, e.g., Realtek).
      • GPU drivers (Intel or NVIDIA).
  • Network Drivers:
    • Wi-Fi or Ethernet drivers can also contribute. Try downloading the latest driver for your network adapter.

2. Adjust Power Settings in Windows​

Aggressive power-saving features can worsen DPC latency.
  • Open Control Panel > Power Options.
  • Select High Performance or Ultimate Performance (if present).
  • Click Change plan settings > Change advanced power settings, then:
    • Expand Processor power management:
    • Set Minimum processor state to 100%.
    • Disable USB selective suspend.
    • Disable Link State Power Management under PCI Express.

3. Tweak the BIOS Settings​

Some XPS models see improvements when you adjust or disable certain BIOS features.
Steps:
  1. Enter BIOS/UEFI (usually F2 during boot).
  2. Look for and disable:
    • C-States or CPU C-State Control.
    • Intel SpeedStep (if disabling doesn’t cause thermal issues, try re-enabling afterward for testing).
  3. Save and reboot.
Be cautious—BIOS changes can improve or worsen stability depending on your specific device configuration.

4. Test with LatencyMon​

Using LatencyMon (a free tool), you can confirm improvements after each change.

5. Disable Dynamic Platform and Thermal Framework (DPTF)​

Intel’s DPTF is notorious for throttling and can interfere with overall system responsiveness.
  • Temporarily test disabling this by:
    • Open Device Manager (Win + X > Device Manager).
    • Expand System Devices.
    • Locate Intel Dynamic Platform and Thermal Framework components.
    • Right-click on each and Disable device (reboot to apply).
Note: Disabling DPTF may increase heat buildup and reduce battery life—monitor your system after testing.

6. Advanced Option: Undervolt Your CPU​

Undervolting the CPU can reduce background spikes caused by power transitions while keeping performance intact. Use tools like ThrottleStop or Intel XTU (depending on CPU generation).
Pro Tip: Dell often locks undervolting in recent BIOS versions, so check if it’s possible before diving in.

If All Else Fails: External Soundcard or DAC​

If ACPI.sys persists as an issue despite all these optimizations, consider using an external USB DAC/soundcard. These devices bypass system-level latency issues and provide a cleaner, more reliable audio path.

Final Notes​

DPC latency battles are tedious, but focusing on driver updates and power settings often yields noticeable improvements. Let us know what you've tried, and I’m happy to explore more advanced steps with you if needed.
 
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