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[57Gregy]

Is it a Dell?
 

[Steve Moddelmog]

25 minutes ago, 57Gregy said:

Is it a Dell?
 

No, it's an HP.

[Steve Moddelmog]

16 hours ago, bitflipper said:

I've seen complaints about ACPI.sys having excessive DPC latency before. Usually on laptops, usually having something to do with power settings. You might try some different power schemes, just to see if it makes any difference. Make sure that sleep mode is completely disabled. I've always used the "High Performance" power preset, which, iirc, disables sleep mode. Also go into the Advanced power settings, expand the USB Settings category and verify that USB suspend is disabled (assuming your interface is connected via USB).

ACPI does more than just power management, though. (Well, technically ACPI doesn't do anything on its own, as it's a driver that interfaces with your BIOS. The idea is that ACPI.sys lets you change certain BIOS settings directly from Windows that in the old days would have required booting into the BIOS.) It might be worth booting into the BIOS and poking around in there. It may allow you to disable ACPI.

Power settings are all at their most "generous."  USB not allowed to turn off to save power. I have never used sleep, and the first thing I do when i get a new computer is disable hibernate.  At your suggestion, I looked at BIOS settings but I didn't see anything there that seemed to relate to power settings, other than an optimize battery setting which I didn't think would make a difference but I disabled it anyway (it was enabled).  I do let Windows turn my screen off after X minutes of inactivity.  Wouldn't think that would be problematic, would it?

[Steve Moddelmog]

I asked Google Bard for help with this issue.  Here's what I got - unfortunately nothing helpful:

How can I keep acpi.sys from causing latency in music production software?

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The acpi.sys driver is responsible for managing power consumption on your computer. It can sometimes cause latency in music production software, which can lead to clicks, pops, and other audio problems. There are a few things you can do to keep acpi.sys from causing latency:

Update your drivers. Make sure you have the latest drivers for your computer's motherboard, processor, and graphics card. You can usually find these drivers on the manufacturer's website.

Disable power management. Go to Control Panel > Hardware and Sound > Device Manager. Expand the "System Devices" category and right-click on "ACPI-Compliant System". Select "Properties" and go to the "Power Management" tab. Uncheck the box next to "Allow the computer to turn off this device to save power".

Use a dedicated audio interface. A dedicated audio interface will give you much lower latency than your computer's built-in sound card. This will help to prevent acpi.sys from causing problems with your music production software.

If you are still experiencing latency problems after trying these steps, you may need to contact your computer manufacturer or audio interface manufacturer for further assistance.

Here are some additional tips for reducing DPC latency:

Use a high-quality power supply. A poor-quality power supply can cause all sorts of problems with your computer's performance, including DPC latency.

Keep your computer cool. Heat can also cause DPC latency, so make sure your computer has good ventilation.

Close unnecessary programs. Any programs that are running in the background can contribute to DPC latency. Close any programs that you are not using.

Defragment your hard drive. A fragmented hard drive can also cause DPC latency. Defragment your hard drive regularly to improve performance.

By following these tips, you can help to reduce DPC latency and improve the performance of your music production software.

[Steve Moddelmog]

And here is Bing's answer:

It seems that acpi.sys is a common source of DPC latency for many users who want to use their laptops for music production. According to some online forums123, there are a few possible solutions you can try:

Perform a clean install of Windows 10 and update all your drivers and BIOS2.

Set your power mode to best performance and adjust the minimum processor state to 100% in the advanced power settings24.

Turn off C-states, Intel TurboBoost, Intel Speedstep, and Intel Speed Shift in the BIOS2.

Disable or uninstall any unnecessary devices or programs that may cause interference, such as ACPI-Compliant Control Method battery, Intel Dynamic Platform & Thermal Framework, Bonjour, MaxxAudioPro, OneDrive, etc2.

Use a third-party program like Process Lasso or Process Hacker to set the process affinity or suspend the ACPI.sys threads25.

Switch to a different audio interface with better drivers, such as Scarlett 18i83.

I hope this helps you with your problem.

[bitflipper]

I let Windows turn off my screen, too. A habit going back to burn-in concerns on CRTs. I do have the timer set to a long time (2 hours, I think) to avoid the annoyance of having it go black when I'm just looking at it. So no, I don't think blanking the display would have any effect. What you're seeing is overhead from changing some setting, e.g. a disk drive spinning back up after a power-saving shutdown (probably not your problem, given it's an SSD). 

Thinking about it further, it seems the DPC has to be in response to the BIOS doing something and alerting Windows of the change. One of those would be throttling the CPU clock speed to save power (aka SpeedStep). This feature can be turned off in the BIOS. Note that your BIOS may call it something else, e.g. "Cool 'n Quiet" (AMD).

Although Cakewalk does recommend disabling SpeedStep, it should normally not be a problem and it isn't the kind of thing that happens continuously. It normally wouldn't be triggering many interrupts like you're seeing - unless your computer has a heat problem. It might be worthwhile to check how hot your CPU is running. There are several free tools for taking your CPU's temperature. I use CoreTemp. What's a good temperature? A rule of thumb is < 80 degrees C, but some CPUs routinely run hotter. Some are fine running up 100 degrees C.

[Steve Moddelmog]

4 minutes ago, bitflipper said:

I let Windows turn off my screen, too. A habit going back to burn-in concerns on CRTs. I do have the timer set to a long time (2 hours, I think) to avoid the annoyance of having it go black when I'm just looking at it. So no, I don't think blanking the display would have any effect. What you're seeing is overhead from changing some setting, e.g. a disk drive spinning back up after a power-saving shutdown (probably not your problem, given it's an SSD). 

Thinking about it further, it seems the DPC has to be in response to the BIOS doing something and alerting Windows of the change. One of those would be throttling the CPU clock speed to save power (aka SpeedStep). This feature can be turned off in the BIOS. Note that your BIOS may call it something else, e.g. "Cool 'n Quiet" (AMD).

Although Cakewalk does recommend disabling SpeedStep, it should normally not be a problem and it isn't the kind of thing that happens continuously. It normally wouldn't be triggering many interrupts like you're seeing - unless your computer has a heat problem. It might be worthwhile to check how hot your CPU is running. There are several free tools for taking your CPU's temperature. I use CoreTemp. What's a good temperature? A rule of thumb is < 80 degrees C, but some CPUs routinely run hotter. Some are fine running up 100 degrees C.

I don't see anything in the BIOS settings that looks like it has to do with CPU throttling - I can pretty much tell what everything is for and there's just nothing like that.  Maybe having no setting is HP's intention for this model.

Thanks for the link to CoreTemp.  I downloaded it, and the "hottest" Core (Core 0) is currently 69 degrees C.

[bitflipper]

9 minutes ago, Steve Moddelmog said:

Switch to a different audio interface with better drivers, such as Scarlett 18i83.

This has nothing to do with your problem.

[bitflipper]

3 minutes ago, Steve Moddelmog said:

the "hottest" Core (Core 0) is currently 69 degrees C.

That's certainly not a problem, then.

Well, you gotta knock down the possible explanations one at a time. It may seem like you've made no progress, but you have: at this point you do know that it's a hardware problem.