System Interrupts causing high CPU usage on a tablet after pressing the hardware Start button

Question

Hello, I have an ASUS T100TA tablet (Z3740, 32GB, no HDD in dock) with Windows 8.1 on it, fully updated.

BIOS version is up to date (313), all drivers are updated from ASUS website.

I have the following problem: In certain conditions, the process called "System Interrupts" would take 8-25% of CPU time until the system is rebooted. It always happens after pressing the hardware Start button located on the left side of the tablet. I found a way to reproduce this problem by doing the following:

1. Make sure "Fast Startup" is on, restart the device.
2. Shut down the device like usual.
3. Turn it back on, fire up Task Manager and press the Windows key on the left side of the device. System Interrupts is now taking 8-25% of CPU cycles.

I used Process Explorer and found out that the driver responsible for CPU spikes was sdbus.sys.

This issue affects a large number of T100TA users, as you can see

in this thread.

Some people claim that updating BIOS and Intel SoC driver helps, but it is due to the specific conditions that trigger the problem that they don't realize the problem is still there. Since you are usually forced to restart after installing Intel SoC drivers, the problem goes away. It only shows up if you have shut down the machine (with Fast Startup on) at least once and then pressed the hardware Start button.

I believe this may be a bug in Windows or Intel Bay Trail drivers. It happens on a clean Windows 8.1 install too, as soon as you have the Intel SoC drivers installed, no matter which version.

Could you please look into it and see what can be done? If you need any more information, please let me know.

Answer 1

To anyone who stumbles upon this thread: yes, this problem has never been fixed and is still there in all Windows versions starting from Windows 8 onwards, including Windows 10 build 10240.

Answer 2

There is one more problem hitting all T100's, problem with UHS-I microSD cards dissapearing from device manager/my computer when tablet goes to sleep. Some T100's won't even detect UHS-I microSD cards at all, however some UHS-I cards work fine, so it's a lottery with this tablet.

Answer 3

Sent my tablet back to ASUS, got a new one with exactly the same issue. It even occurs on Windows 10 Technological Preview.

Answer 4

I have tried all methods listed above and the issue still persists.

1. This is a tablet and it doesn't have any external devices plugged in, except the keyboard dock that goes with it. Even with it unplugged, the same issue persists. Maintenance doesn't help. Restarting fixes the problem, but only until I shut down the computer and start it again (Fast Startup must be enabled), then pressing Start button on the left side of the tablet causes high CPU usage until the next restart. Disabling Fast Startup fixes the issue too, but I need to use this function because it is a tablet.
2. The issue does not occur in Safe Mode only because the drivers associated with the hardware Start button are not loaded in Safe Mode. The hardware button does not work in Safe mode either, obviously.
3. I have excluded the possibility of having any virus infection by reformatting the entire system and clean installing Windows 8.1 from scratch. Also, I have performed a full anti-virus scan, which found nothing. The behavior I described in the first post is more likely to happen due to a bug in a driver rather than a virus.

Answer 5

Hi,

Thank you for posting your question in the Microsoft Community Forums.

This issue might occur due to broken or corrupt system files, missing updates and incompatible or outdated drivers. Sorry to know that you are facing this issue.

Let us follow these methods one by one and check if this helps.

Method 1.

Unplug all external devices connected to the computer and restart the computer to check if this helps.

Further, you may run the System Maintenance troubleshooter and restart the computer to check the status.

a) Press the ‘Windows + C’ to activate the charms menu or move the mouse pointer to bottom right corner of the screen and you will get the charms menu.

b) Click on ‘search’ and select ‘settings’ and type ‘Troubleshooting’ and select ‘Troubleshooting’.

c) On the left pane click "View all" and then click "System Maintenance" and run the troubleshooter.

Once the troubleshooter is run, restart the computer and check the status.

Method 2.

Let us boot the computer in Safe Mode and check if the issue persists. Safe Mode starts Windows with a minimal set of drivers and services.

If you're not signed in to Windows, tap or click the power icon from the sign-in screen, hold the Shift key, and then tap or click Restart.

Windows Startup Settings (including safe mode): http://windows.microsoft.com/en-in/windows-8/windows-startup-settings-safe-mode

If the issue does not persists in Safe Mode, then perform a clean boot state and check if the issue persists.

When you start Microsoft Windows, typically there are several programs that start automatically and run in the background that may interfere with the game. These programs may include antivirus and system utility programs. When you perform a clean startup procedure, you prevent these programs from starting automatically.

How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7, Windows 8:http://support.microsoft.com/kb/929135

Note: After you have finished troubleshooting, follow steps under “How to reset the computer to start as usual after troubleshooting with clean boot” in the article to boot to normal startup.

Method 3.

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Sometimes due to virus infection the computer might not act or work as it should. You may perform a full computer virus scan using Windows Defender to ensure that the computer is free from virus.

How do I find and remove a virus?: http://windows.microsoft.com/en-in/windows-8/how-find-remove-virus

Safety Scanner Disclaimer: There could be a loss of data while performing a scan using Microsoft safety scanner to eliminate virus if any.

Reply with the status of the issue and we will be glad to offer our assistance.