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Unfortunately by design Windows is not a real-time operating system, Real-time audio processing in Windows requires a fine tuned and reactive system.
Some drivers or devices may interrupt the data processing for too long, which results in drops.
See 
https://en.wikipedia.org/wiki/Deferred_Procedure_Call for details.

Merging recommends you use LatencyMon to check DPC latencies on your system. (Windows 10)

DPCLatencyChecker only works on Windows 7 (false results on Windows 8.1 and 10)

Run the application in "normal" conditions, do not start "big" programs, do not install new drivers,...
Let LatencyMon run for at least 10 minutes (Merging recommends 30 minutes, or more).

If the DPC does not report problems
All green and no faults your system should be adequate to perform realtime audio tasks.


If DPC Errors and realtime Audio problems:

  • If you get DPC errors, see the reported driver name to be able to track the culprit.
    Follow LatencyMon documentation to perform the investigation http://www.resplendence.com/latencymon_using
  • First step to solve such issue is usually to update the device driver (if possible). 
    Note: At times Windows does not detect the new driver and users might be required to go to the component manufacturer website.
  • If updating the driver does not help, or if no newer driver exists, you will have to disable the device in Windows device manager.
    Warning: Don't disable devices that are essential for your computer to function!
    Do NOT disable:
    -any device listed in Device Manager under System devices or Computer,
    -the hard disk that contains the system partition,
    -the IDE/ATAPI /SATA/RAID controller this hard disk is connected to,
    -the system keyboard,
    -the mouse, track point or touch pad device,
    -the USB controller external keyboard and/or mouse devices are connected to,
    -the display controller listed under Display adapters.
  • If disabling the device does not help or is not possible, you can check if Windows is running a specific task or service that triggers the issue.
    When you get a spike, go in Windows Event viewer > Windows logs.
    You should first check in Application and System if you see errors at the time you had the spike. 
    From there you might get more information on the process / service that is triggering the issue.
    Again, make sure you do not disable an essential service or task for Windows to run !


DPC Latency Mon helper
Most complete guide to DPC latency faults.

https://www.resplendence.com/latencymon_using


BIOS

In some case, DPC Latency is reporting failure related to the BIOS configuration.(screenshot below)

Depending of your configuration and if you have access to the BIOS, the settings below are quite important (those might not be acessible with some laptops).

For most accurate results you should disable variable clock speed settings in your BIOS setup such as.

Please have a look at your motherboard manual to locate those settings, may vary depending of the manufacturer.

Intel Turbo Boost Technology: Disabled
CPU Enhanced Halt (C1E): Disabled
C-State Support (C3, C6, C7, C8 State): all Disabled 
CPU EIST Function: Disabled (also called Intel Enhanced SpeedStep, that should always be disabled) 
CPU power saving mode: Disabled

AMD Cool N Quiet:  Disabled 

MassCore users : Secure Boot option is not supported, please disable this feature in your BIOS.



Windows 10 configuration

Merging also has Windows 10 recommendation for the system configurations.

https://confluence.merging.com/display/PUBLICDOC/Windows+10+Configuration