acpi.sys

Windows ACPI System Driver

System DriverSafePower Management

CPU Usage

0-2%

Memory

2-10 MB

Location

C:\Windows\System32\drivers

Publisher

Microsoft Corporation

Quick Answer

acpi.sys is a legitimate Windows system driver. It manages ACPI power states, sleep/wake transitions, and thermal management across hardware.

Is it a Virus?

✔ NO - Safe

Must be located in C:\Windows\System32\drivers\ACPI.sys

Warning

Occasional driver updates

System may restart to apply ACPI driver updates

Can I Disable?

✖ NO

Disabling ACPI.sys can render sleep/hibernate non-functional; update instead

What is acpi.sys?

acpi.sys is the Windows Advanced Configuration and Power Interface (ACPI) system driver responsible for hardware power states, sleep transitions, and thermal management. It operates in kernel mode to coordinate with BIOS/UEFI power tables and manage modern hardware power features across devices.

ACPI.sys translates OS power policies into hardware commands, handling sleep, wake, thermal throttling, battery reporting, and device power gating. As a core kernel component, it runs continually to support stable power management across diverse hardware setups.

Quick Fact: ACPI standardization enables cross-vendor power features; acpi.sys implements these interfaces to coordinate sleep states and device power across modern laptops and desktops.

Types of ACPI-Related Driver Roles

System Driver: Core power management interfacing with hardware
Power State Manager: S1-S5 state transitions and sleep behavior
Thermal Controller: Reads thermal sensors and regulates cooling
Platform Firmware Interface: Bridges OS with BIOS/UEFI ACPI tables

Is acpi.sys Safe?

Yes, acpi.sys is safe when it’s the legitimate Windows driver located in C:\Windows\System32\drivers and signed by Microsoft.

Is acpi.sys a Virus or Malware?

The genuine acpi.sys is not malware. Malware may masquerade with similar names, so verify digital signatures and path.

How to Tell if acpi.sys is Legitimate or Malware

File Location: Must be in C:\Windows\System32\drivers\ACPI.sys. Any acpi.sys elsewhere is suspicious.
Digital Signature: Right-click the file in Explorer → Properties → Digital Signatures. Should show 'Microsoft Windows' as signer.
Driver Details: Open Device Manager > System Devices; locate ACPI or Microsoft ACPI; verify driver provider is Microsoft.
System Behavior: If you cannot sleep or wake properly, investigate with Windows Event Viewer and update drivers.

Red Flags: ACPI.sys in non-standard folders (like Temp/TempFolder), unsigned drivers, or multiple conflicting ACPI drivers indicate tampering or corruption.

Why Is acpi.sys Running on My PC?

acpi.sys is active to coordinate system power policies and hardware state changes. It runs as part of Windows power management to support sleep, wake, and thermal control.

Reasons it's running:

Active Sleep/Wake Transitions: System transitions to and from sleep/hibernation require ACPI state management by the driver.
Thermal Management: Fan control and thermal throttling depend on ACPI data from sensors.
Battery and Power Plans: Laptop power plans and battery reporting rely on ACPI to report charge levels and suspend behavior.
Firmware Interface: ACPI provides a bridge to BIOS/UEFI for platform-specific power features.
Hardware Configuration Changes: Changing hardware (RAM, PCIe devices) may trigger ACPI reconfiguration and driver activity.

Can I Disable or Remove acpi.sys?

No, you should not disable acpi.sys. It is essential for safe power management and sleep functionality. You can update or roll back drivers if issues occur.

How to Troubleshoot Without Disabling

Update BIOS/UEFI: Check manufacturer support site for the latest firmware and install according to their instructions.
Update Windows: Run Windows Update to obtain the latest system drivers and ACPI improvements.
Run Power Troubleshooter: Windows Settings > Troubleshoot > Additional troubleshooters > Power.
Check Sleep Settings: Settings > System > Power & sleep; adjust sleep/hibernate timings and disable hybrid sleep if needed.
Review Event Logs: Event Viewer > Windows Logs > System; look for ACPI or power management warnings.

How to Remove acpi.sys

✔ Do not uninstall; this is a core driver. If needed, refresh Windows or perform an in-place repair via Windows Installation Media.

Common Problems: Power or Sleep Issues

If acpi.sys is causing power or sleep problems, try targeted fixes below.

Common Causes & Solutions

Sleep not turning on: Update BIOS/UEFI and Windows power settings; ensure Sleep states are enabled in BIOS.
System won't wake from sleep: Disable wake timers in Power Options and update drivers for motherboard/chipset.
High battery drain: Check for background devices; calibrate battery and update ACPI drivers.
Random reboot during sleep: Run sfc /scannow, check Event Viewer, and ensure BIOS/firmware is current.
Fan running constantly: Update firmware and check for thermal throttling; adjust power plan to balanced.
ACPI driver errors in Event Viewer: Update Windows and chipset drivers; consider System File Checker.

Quick Fixes:
1. Run Windows Update to ensure latest drivers
2. Update BIOS/UEFI firmware from the manufacturer
3. Run Power Troubleshooter in Windows
4. Reset power plan to balanced
5. Scan for corrupt system files with sfc /scannow

Frequently Asked Questions

Is acpi.sys a virus?

No, acpi.sys is a legitimate Windows system driver located in C:\Windows\System32\drivers and signed by Microsoft. Malware can masquerade as this name, so verify the path and signature.

What does acpi.sys do?

acpi.sys handles Advanced Configuration and Power Interface functions, including sleep/hibernate transitions, thermal management, and battery reporting for modern hardware.

Can I disable acpi.sys?

Disabling acpi.sys is not recommended; it may break sleep/hibernate and power management. Update BIOS and chipset drivers instead.

Why is my computer not sleeping properly?

Outdated BIOS, conflicting drivers, or misconfigured power settings can prevent sleep. Update firmware, reset power options, and check Event Viewer for ACPI errors.

How can I update or repair acpi.sys?

Install the latest Windows updates, update motherboard chipset drivers, and perform an in-place repair if you suspect system file corruption.

Where is acpi.sys located?

C:\Windows\System32\drivers\ACPI.sys is the standard location. Any other path is suspicious.

What should I do if sleep/wake issues persist?

Check for BIOS updates, run Windows Power Troubleshooter, review Event Viewer logs, and consider a clean boot to identify conflicting software.