The ASUS Gaming Laptop ACPI Firmware Bug: A Deep Technical Investigation
If You're Here, You Know The Pain
You own a high-end ASUS ROG laptop perhaps a Strix, Scar, or Zephyrus. It's specifications are impressive: an RTX 30/40 series GPU, a top-tier Intel processor, and plenty of RAM. Yet, it stutters during basic tasks like watching a YouTube video, audio crackles and pops on Discord calls, the mouse cursor freezes for a split second, just long enough to be infuriating.
You've likely tried all the conventional fixes:
Updating every driver imaginable, multiple times.
Performing a "clean" reinstallation of Windows.
Disabling every conceivable power-saving option.
Manually tweaking processor interrupt affinities.
Following convoluted multi-step guides from Reddit threads.
Even installing Linux, only to find the problem persists.
If none of that worked, it's because the issue isn't with the operating system or a driver. The problem is far deeper, embedded in the machine's firmware, the BIOS.
Initial Symptoms and Measurement
The Pattern Emerges
The first tool in any performance investigator's toolkit for these symptoms is LatencyMon. It acts as a canary in the coal mine for system-wide latency issues. On an affected ASUS Zephyrus M16, the results are immediate and damning:
CONCLUSION Your system appears to be having trouble handling real-time audio and other tasks. You are likely to experience buffer underruns appearing as drop outs, clicks or pops. HIGHEST MEASURED INTERRUPT TO PROCESS LATENCY Highest measured interrupt to process latency (μs): 65,816.60 Average measured interrupt to process latency (μs): 23.29 HIGHEST REPORTED ISR ROUTINE EXECUTION TIME Highest ISR routine execution time (μs): 536.80 Driver with highest ISR routine execution time: ACPI.sys HIGHEST REPORTED DPC ROUTINE EXECUTION TIME Highest DPC routine execution time (μs): 5,998.83 Driver with highest DPC routine execution time: ACPI.sys
The data clearly implicates ACPI.sys . However, the per-CPU data reveals a more specific pattern:
CPU 0 Interrupt cycle time (s): 208.470124 CPU 0 ISR highest execution time (μs): 536.804674 CPU 0 DPC highest execution time (μs): 5,998.834725 CPU 0 DPC total execution time (s): 90.558238
CPU 0 is taking the brunt of the impact, spending over 90 seconds processing interrupts while other cores remain largely unaffected. This isn't a failure of load balancing; it's a process locked to a single core.
A similar test on a Scar 15 from 2022 shows the exact same culprit: high DPC latency originating from ACPI.sys .
It's easy to blame a Windows driver, but ACPI.sys is not a typical driver. It primarily functions as an interpreter for ACPI Machine Language (AML), the code provided by the laptop's firmware (BIOS). If ACPI.sys is slow, it's because the firmware is feeding it inefficient or flawed AML code to execute. These slowdowns are often triggered by General Purpose Events (GPEs) and traffic from the Embedded Controller (EC). To find the true source, we must dig deeper.
Capturing the Problem in More Detail: ETW Tracing
Setting Up Advanced ACPI Tracing
To understand what ACPI.sys is doing during these latency spikes, we can use Event Tracing for Windows (ETW) to capture detailed logs from the ACPI providers.
# Find the relevant ACPI ETW providers logman query providers | findstr / i acpi # This returns two key providers: # Microsoft-Windows-Kernel-Acpi {C514638F-7723-485B-BCFC-96565D735D4A} # Microsoft-ACPI-Provider {DAB01D4D-2D48-477D-B1C3-DAAD0CE6F06B} # Start a comprehensive trace session logman start ACPITrace - p {DAB01D4D - 2D48 - 477D - B1C3 - DAAD0CE6F06B} 0xFFFFFFFF 5 - o C:\Temp\acpi.etl - ets logman update ACPITrace - p {C514638F - 7723 - 485B - BCFC - 96565D735D4A} 0xFFFFFFFF 5 - ets # Then once we're done we can stop the trace and check the etl file and save the data in csv format aswell. logman stop ACPITrace - ets tracerpt C:\Temp\acpi_providers.etl - o C:\Temp\acpi_events.csv - of CSV
An Unexpected Discovery
Analyzing the resulting trace file in the Windows Performance Analyzer reveals a crucial insight. The spikes aren't random; they are periodic, occurring like clockwork every 30 to 60 seconds.
Random interruptions often suggest hardware faults or thermal throttling. A perfectly repeating pattern points to a systemic issue, a timer or a scheduled event baked into the system's logic.
The raw event data confirms this pattern:
Clock-Time (100ns), Event, Kernel(ms), CPU 134024027290917802, _GPE._L02 started, 13.613820, 0 134024027290927629, _SB...BAT0._STA started, 0.000000, 4 134024027290932512, _GPE._L02 finished, -, 6
The first event, _GPE._L02 , is an interrupt handler that takes 13.6 milliseconds to execute. For a high-priority interrupt, this is an eternity and is catastrophic for real-time system performance.
Deeper in the trace, another bizarre behavior emerges; the system repeatedly attempts to power the discrete GPU on and off, even when it's supposed to be permanently active.
Clock-Time, Event, Duration 134024027315051227, _SB.PC00.GFX0._PS0 start, 278μs # GPU Power On 134024027315155404, _SB.PC00.GFX0._DOS start, 894μs # Display Output Switch 134024027330733719, _SB.PC00.GFX0._PS3 start, 1364μs # GPU Power Off [~15 seconds later] 134024027607550064, _SB.PC00.GFX0._PS0 start, 439μs # Power On Again! 134024027607657368, _SB.PC00.GFX0._DOS start, 1079μs # Display Output Switch 134024027623134006, _SB.PC00.GFX0._PS3 start, 394μs # Power Off Again! ...
Why This Behavior is Fundamentally Incorrect
This power cycling is nonsensical because the laptop is configured for a scenario where it is impossible: The system is in Ultimate Mode (via a MUX switch) with an external display connected.
In this mode:
The discrete NVIDIA GPU (dGPU) is the only active graphics processor.
active graphics processor. The integrated Intel GPU (iGPU) is completely powered down and bypassed.
The dGPU is wired directly to the internal and external displays.
There is no mechanism for switching between GPUs.
Yet, the firmware is relentlessly trying to power cycle the dGPU every 15-30 seconds. The dGPU in mux mode isn't just "preferred" - it's the ONLY path to the display. There's no fallback, and no alternative. When the firmware sends _PS3 (power off), it's attempting something architecturally impossible.
Most of the time, hardware sanity checks refuse these nonsensical commands, but even failed attempts introduce latency spikes causing audio dropouts, input lag, and accumulating performance degradation. Games freeze mid-session, videos buffer indefinitely, system responsiveness deteriorates until restart.
The Catastrophic Edge Case
Sometimes, under specific thermal conditions or race conditions, the power-down actually succeeds. When the firmware manages to power down the GPU that's driving the display, the sequence is predictable and catastrophic:
Firmware executes _PS3 - GPU power off command Hardware complies - safety checks fail or timing aligns Display signal cuts - monitors go black User input triggers wake - mouse/keyboard activity Windows calls PowerOnMonitor() - attempt display recovery NVIDIA driver executes _PS0 - GPU power on command GPU enters impossible state - firmware insists OFF, Windows needs ON Driver thread blocks indefinitely - waiting for GPU response 30-second watchdog expires - Windows gives up System crashes with BSOD
5: kd> !analyze -v ******************************************************************************* * * * Bugcheck Analysis * * * ******************************************************************************* WIN32K_POWER_WATCHDOG_TIMEOUT (19c) Win32k did not turn the monitor on in a timely manner. Arguments: Arg1: 0000000000000050, Calling monitor driver to power on. Arg2: ffff8685b1463080, Pointer to the power request worker thread. Arg3: 0000000000000000 Arg4: 0000000000000000 ... STACK_TEXT: fffff685`3a767130 fffff800`94767be0 : 00000000`00000047 00000000`00000000 00000000`00000000 00000000`00000000 : nt!KiSwapContext+0x76 fffff685`3a767270 fffff800`94726051 : ffff8685`b1463080 00000027`00008b94 fffff685`3a767458 fffff800`00000000 : nt!KiSwapThread+0x6a0 fffff685`3a767340 fffff800`94724ed3 : fffff685`00000000 00000000`00000043 00000000`00000002 0000008a`fbf50968 : nt!KiCommitThreadWait+0x271 fffff685`3a7673e0 fffff800`9471baf2 : fffff685`3a7675d0 02000000`0000001b 00000000`00000000 fffff800`94724500 : nt!KeWaitForSingleObject+0x773 fffff685`3a7674d0 fffff800`9471b7d5 : ffff8685`9cbec810 fffff685`3a7675b8 00000000`00010224 fffff800`00000003 : nt!ExpWaitForFastResource+0x92 fffff685`3a767580 fffff800`9471b49d : 00000000`00000000 ffff8685`9cbec850 ffff8685`b1463080 00000000`00000000 : nt!ExpAcquireFastResourceExclusiveSlow+0x1e5 fffff685`3a767630 fffff800`28faca9b : fffff800`262ee9c8 00000000`00000003 ffff8685`9cbec810 02000000`00000065 : nt!ExAcquireFastResourceExclusive+0x1bd fffff685`3a767690 fffff800`28facbe5 : ffff8685`b31de000 00000000`00000000 ffffd31d`9a05244f 00000000`00000000 : win32kbase!::+0x2b fffff685`3a7676c0 fffff800`28e5f864 : ffffad0c`94d10878 fffff685`3a767769 ffffad0c`94d10830 ffff8685`b31de000 : win32kbase!UserCritInternal::`anonymous namespace'::EnterCritInternalEx+0x4d fffff685`3a7676f0 fffff800`28e5f4ef : 00000000`00000000 00000000`00000000 fffff800`262ee9c8 00000000`00000000 : win32kbase!DrvSetWddmDeviceMonitorPowerState+0x354 fffff685`3a7677d0 fffff800`28e2abab : ffff8685`b31de000 00000000`00000000 ffff8685`b31de000 00000000`00000000 : win32kbase!DrvSetMonitorPowerState+0x2f fffff685`3a767800 fffff800`28ef22fa : 00000000`00000000 fffff685`3a7678d9 00000000`00000001 00000000`00000001 : win32kbase!PowerOnMonitor+0x19b fffff685`3a767870 fffff800`28ef13dd : ffff8685`94a40700 ffff8685`a2eb31d0 00000000`00000001 00000000`00000020 : win32kbase!xxxUserPowerEventCalloutWorker+0xaaa fffff685`3a767940 fffff800`4bab21c2 : ffff8685`b1463080 fffff685`3a767aa0 00000000`00000000 00000000`00000020 : win32kbase!xxxUserPowerCalloutWorker+0x13d fffff685`3a7679c0 fffff800`26217f3a : 00000000`00000000 00000000`00000000 00000000`00000000 00000000`00000000 : win32kfull!NtUserUserPowerCalloutWorker+0x22 fffff685`3a7679f0 fffff800`94ab8d55 : 00000000`000005bc 00000000`00000104 ffff8685`b1463080 00000000`00000000 : win32k!NtUserUserPowerCalloutWorker+0x2e fffff685`3a767a20 00007ff8`ee71ca24 : 00000000`00000000 00000000`00000000 00000000`00000000 00000000`00000000 : nt!KiSystemServiceCopyEnd+0x25 000000cc`d11ffbc8 00000000`00000000 : 00000000`00000000 00000000`00000000 00000000`00000000 00000000`00000000 : 0x00007ff8`ee71ca24 ...
The crash dump confirms the thread is stuck in win32kbase!DrvSetWddmDeviceMonitorPowerState , waiting for the NVIDIA driver to respond. It can't because it's caught between a confused power state, windows wanting to turn on the GPU while the firmware is arming the GPU cut off.
Understanding General Purpose Events
GPEs are the firmware's mechanism for signaling hardware events to the operating system. They are essentially hardware interrupts that trigger the execution of ACPI code. The trace data points squarely at _GPE._L02 as the source of our latency.
A closer look at the timing reveals a consistent and problematic pattern:
_GPE._L02 Event Analysis from ROG Strix Trace: Event 1 @ Clock 134024027290917802 Duration: 13,613,820 ns (13.61ms) Triggered: Battery and AC adapter status checks Event 2 @ Clock 134024027654496591 Duration: 13,647,255 ns (13.65ms) Triggered: Battery and AC adapter status checks Event 3 @ Clock 134024028048493318 Duration: 13,684,515 ns (13.68ms) Triggered: Battery and AC adapter status checks Interval between events: ~36-39 seconds Consistency: The duration is remarkably stable and the interval is periodic.
The Correlation
Every single time the lengthy _GPE._L02 event fires, it triggers the exact same sequence of ACPI method calls.
The pattern is undeniable:
A hardware interrupt fires _GPE._L02 . The handler executes methods to check battery status. Shortly thereafter, the firmware attempts to change the GPU's power state. The system runs normally for about 30-60 seconds. The cycle repeats.
Extracting and Decompiling the Firmware Code
Getting to the Source
To analyze the code responsible for this behavior, we must extract and decompile the ACPI tables provided by the BIOS to the operating system.
# Extract all ACPI tables into binary .dat files acpidump -b # Output includes: # DSDT.dat - The main Differentiated System Description Table # SSDT1.dat ... SSDT17.dat - Secondary System Description Tables # Decompile the main table into human-readable ACPI Source Language (.dsl) iasl -d DSDT.dsl
This decompiled ASL provides a direct view into the firmware's executable logic. It is a precise representation of the exact instructions that the ACPI.sys driver is fed by the firmware and executes at the highest privilege level within the Windows kernel. Any logical flaws found in this code are the direct cause of the system's behavior.
Finding the GPE Handler
Searching the decompiled DSDT.dsl file, we find the definition for our problematic GPE handler:
Scope ( _GPE ) { Method ( _L02 , 0 , NotSerialized ) // _Lxx: Level-Triggered GPE { \ _SB .PC00.LPCB.ECLV () } }
This code is simple: when the _L02 interrupt occurs, it calls a single method, ECLV . The "L" prefix in _L02 signifies that this is a level-triggered interrupt, meaning it will continue to fire as long as the underlying hardware condition is active. This is a critical detail.
The Catastrophic ECLV Implementation
Following the call to ECLV() , we uncover a deeply flawed implementation that is the direct cause of the system-wide stuttering.
Method (ECLV, 0 , NotSerialized ) // Starting at line 099244 { // Main loop - continues while events exist OR sleep events are pending // AND we haven't exceeded our time budget (TI3S < 0x78) While (((CKEV() != Zero ) || (SLEC != Zero )) && (TI3S < 0x78 )) { Local1 = One While ( Local1 != Zero ) { Local1 = GEVT() // Get next event from queue LEVN ( Local1 ) // Process the event TIMC += 0x19 // Increment time counter by 25 // This is where it gets really bad If ((SLEC != Zero ) && ( Local1 == Zero )) { // No events but sleep events pending If (TIMC == 0x19 ) { Sleep ( 0x64 ) // Sleep for 100 milliseconds!!! TIMC = 0x64 // Set time counter to 100 TI3S += 0x04 // Increment major counter by 4 } Else { Sleep ( 0x19 ) // Sleep for 25 milliseconds!!! TI3S++ // Increment major counter by 1 } } } } // Here's where it gets even worse If (TI3S >= 0x78 ) // If we hit our time budget (120) { TI3S = Zero If (EEV0 == Zero ) { EEV0 = 0xFF // Force another event to be pending! } } }
Breaking Down this monstrosity
This short block of code violates several fundamental principles of firmware and kernel programming.
Wtf 1: Sleeping in an Interrupt Context
Sleep ( 0x64 ) // 100ms sleep Sleep ( 0x19 ) // 25ms sleep
An interrupt handler runs at a very high priority to service hardware requests quickly. The Sleep() function completely halts the execution of the CPU core it is running on (CPU 0 in this case). While CPU 0 is sleeping, it cannot:
Process any other hardware interrupts.
Allow the kernel to schedule other threads.
Update system timers.
Wtf 2: Time-Sliced Interrupt Processing The entire loop is designed to run for an extended period, processing events in batches. It's effectively a poorly designed task scheduler running inside an interrupt handler, capable of holding a CPU core hostage for potentially seconds at a time.
Wtf 3: Self-Rearming Interrupt
If (EEV0 == Zero ) { EEV0 = 0xFF // Forces all EC event bits on }
This logic ensures that even if the Embedded Controller's event queue is empty, the code will create a new, artificial event. This guarantees that another interrupt will fire shortly after, creating the perfectly periodic pattern of ACPI spikes observed in the traces.
The Event Dispatch System
How Events Route to Actions
The LEVN() method takes an event and routes it:
Method (LEVN, 1 , NotSerialized ) { If (( Arg0 != Zero )) { MBF0 = Arg0 P80B = Arg0 Local6 = Match (LEGA, MEQ , Arg0 , MTR , Zero , Zero ) If (( Local6 != Ones )) { LGPA ( Local6 ) } } }
The LGPA Dispatch Table
The LGPA() method is a giant switch statement handling different events:
Method (LGPA, 1 , Serialized ) // Line 098862 { Switch ( ToInteger ( Arg0 )) { Case ( Zero ) // Most common case - power event { DGD2 () // GPU-related function ^EC0._QA0 () // EC query method PWCG () // Power change - this is our battery polling } Case ( 0x18 ) // GPU-specific event { If (M6EF == One ) { Local0 = 0xD2 } Else { Local0 = 0xD1 } NOD2 ( Local0 ) // Notify GPU driver } Case ( 0x1E ) // Another GPU event { Notify (^^PEG1.PEGP, 0xD5 ) // Direct GPU notification ROCT = 0x55 // Sets flag for follow-up } } }
This shows a direct link: a GPE fires, and the dispatch logic calls functions related to battery polling and GPU notifications.
The Battery Polling Function
The PWCG() method, called by multiple event types, is responsible for polling the battery and AC adapter status.
Method (PWCG, 0 , NotSerialized ) { Notify (ADP0, Zero ) // Tell OS to check the AC adapter ^BAT0. _BST () // Execute the Battery Status method Notify (BAT0, 0x80 ) // Tell OS the battery status has changed ^BAT0. _BIF () // Execute the Battery Information method Notify (BAT0, 0x81 ) // Tell OS the battery info has changed }
Which we can see here:
Each of these operations requires communication with the Embedded Controller, adding to the workload inside the already-stalled interrupt handler.
The GPU Notification System
The NOD2() method sends notifications to the GPU driver.
Method (NOD2, 1 , Serialized ) { If (( Arg0 != DNOT)) { DNOT = Arg0 Notify (^^PEG1.PEGP, Arg0 ) } If ((ROCT == 0x55 )) { ROCT = Zero Notify (^^PEG1.PEGP, 0xD1 ) // Hardware-Specific } }
These notifications ( 0xD1 , 0xD2 , etc.) are hardware-specific signals that tell the NVIDIA driver to re-evaluate its power state, which is what triggers the futile _PS0/_DOS/_PS3 power-cycling sequence seen in the traces.
The Mux Mode Confusion: A Firmware with a Split Personality
Here's where a simple but catastrophic oversight in the firmware's logic causes system-wide failure. High-end ASUS gaming laptops feature a MUX (Multiplexer) switch, a piece of hardware that lets the user choose between two distinct graphics modes:
Optimus Mode: The power-saving default. The integrated Intel GPU (iGPU) is physically connected to the display. The powerful NVIDIA GPU (dGPU) only renders demanding applications when needed, passing finished frames to the iGPU to be drawn on screen. Ultimate/Mux Mode: The high-performance mode. The MUX switch physically rewires the display connections, bypassing the iGPU entirely and wiring the NVIDIA dGPU directly to the screen. In this mode, the dGPU is not optional; it is the only graphics processor capable of outputting an image.
Any firmware managing this hardware must be aware of which mode the system is in. Sending a command intended for one GPU to the other is futile and, in some cases, dangerous. Deep within the ACPI code, a hardware status flag named HGMD is used to track this state. To understand the flaw, we first need to decipher what HGMD means, and the firmware itself gives us the key.
Decoding the Firmware's Logic with the Brightness Method
For screen brightness to work, the command must be sent to the GPU that is physically controlling the display backlight. A command sent to the wrong GPU will simply do nothing. Therefore, the brightness control method ( BRTN ) must be aware of the MUX switch state to function at all. It is the firmware's own Rosetta Stone.
// Brightness control - CORRECTLY checks for mux mode Method (BRTN, 1 , Serialized ) // Line 034003 { If (((DIDX & 0x0F0F ) == 0x0400 )) { If (HGMD == 0x03 ) // 0x03 = Ultimate/Mux mode { // In mux mode, notify discrete GPU Notify (\ _SB .PC00.PEG1.PEGP.EDP1, Arg0 ) } Else { // In Optimus, notify integrated GPU Notify (\ _SB .PC00.GFX0.DD1F, Arg0 ) } } }
The logic here is flawless and revealing. The code uses the HGMD flag to make a binary decision. If HGMD is 0x03 , it sends the command to the NVIDIA GPU. If not, it sends it to the Intel GPU. The firmware itself, through this correct implementation, provides the undeniable definition: HGMD == 0x03 means the system is in Ultimate/Mux Mode.
The Logical Contradiction: Unconditional Power Cycling in a Conditional Hardware State
This perfect, platform-aware logic is completely abandoned in the critical code paths responsible for power management. The LGPA method, which is called by the stutter-inducing interrupt, dispatches power-related commands to the GPU without ever checking the MUX mode.
// GPU power notification - NO MUX CHECK! Case ( 0x18 ) { // This SHOULD have: If (HGMD != 0x03) // But it doesn't, so it runs even in mux mode If (M6EF == One ) { Local0 = 0xD2 } Else { Local0 = 0xD1 } NOD2 ( Local0 ) // Notifies GPU regardless of mode }
This is the bug. The firmware, despite proving it knows how to check the MUX state, forgets to do so here. It blindly sends a power-management notification to the NVIDIA driver, instructing it to change power states. In MUX mode, this command is nonsensical it's asking the driver to power down the only GPU that is keeping the screen on. This triggers the futile power-cycling, the massive latency spikes, and the system instability.
Another Path to the Same Problem: The Platform Power Management DSM
This is not a single typo. A second, parallel power management system in the firmware exhibits the exact same flaw. The Platform Extension Plug-in Device ( PEPD ) is used by Windows to manage system-wide power states, such as turning off displays during modern standby.
Device (PEPD) // Line 071206 { Name ( _HID , "INT33A1" ) // Intel Power Engine Plugin Method ( _DSM , 4 , Serialized ) // Device Specific Method { // ... lots of setup code ... // Arg2 == 0x05: "All displays have been turned off" If (( Arg2 == 0x05 )) { // Prepare for aggressive power saving If ( CondRefOf (\ _SB .PC00.PEG1.DHDW)) { ^^PC00.PEG1.DHDW () // GPU pre-shutdown work ^^PC00.PEG1.DGCE = One // Set "GPU Cut Enable" flag } If (S0ID == One ) // If system supports S0 idle { GUAM ( One ) // Enter low power mode } ^^PC00.DPOF = One // Display power off flag // Tell USB controller about display state If ( CondRefOf (\ _SB .PC00.XHCI.PSLI)) { ^^PC00.XHCI.PSLI ( 0x05 ) } } // Arg2 == 0x06: "A display has been turned on" If (( Arg2 == 0x06 )) { // Wake everything back up If ( CondRefOf (\ _SB .PC00.PEG1.DGCE)) { ^^PC00.PEG1.DGCE = Zero // Clear "GPU Cut Enable" } If (S0ID == One ) { GUAM ( Zero ) // Exit low power mode } ^^PC00.DPOF = Zero // Display power on flag If ( CondRefOf (\ _SB .PC00.XHCI.PSLI)) { ^^PC00.XHCI.PSLI ( 0x06 ) } } } }
Once again, the firmware prepares to cut power to the discrete GPU without first checking if it's the only GPU driving the displays. This demonstrates that the Mux Mode Confusion is a systemic design flaw. The firmware is internally inconsistent, leading it to issue self-destructive commands that try to cripple the system.
Cross-System Analysis
Traces from multiple ASUS gaming laptop models confirm this is not an isolated issue.
Scar 15 Analysis
Trace Duration: 4.1 minutes
4.1 minutes _GPE._L02 Events: 7
7 Avg. GPE Duration: 1.56ms (lower, but still unacceptably high)
1.56ms (lower, but still unacceptably high) Avg. Interval: 39.4 seconds (nearly identical periodic nature)
39.4 seconds (nearly identical periodic nature) GPU Power Cycles: 8
Zephyrus M16 Analysis
Trace Duration: 19.9 minutes
19.9 minutes _GPE._L02 Events: 3
3 Avg. GPE Duration: 2.94ms
2.94ms GPU Power Cycles: 197 (far more frequent)
197 (far more frequent) ASUS WMI Calls: 2,370 (a massive number, indicating software amplification)
Microsoft has a built-in "smooth video" check. It plays HD video in full screen and watches for hiccups. If the PC drops frames, crackles, or any driver pauses for more than a few milliseconds, it fails. That’s Microsoft’s baseline for what "smooth" should look like.
Why it matters here:
ASUS firmware is causing millisecond-long pauses. Those pauses are exactly the kind that make this test fail i.e., the same stutters and audio pops regular users notice on YouTube/Netflix and games; this firmware violates fundemental standards.
The Universal Pattern
Despite being different models, all affected systems exhibit the same core flaws:
_GPE._L02 handlers take milliseconds to execute instead of microseconds. The GPEs trigger unnecessary battery polling. The firmware attempts to power cycle the GPU while in a fixed MUX mode. The entire process is driven by a periodic, timer-like trigger.
Summarizing the Findings
This bug is a cascade of firmware design failures.
Root Cause 1: The Misunderstanding of Interrupt Context
The firmware's ECLV() method treats a high-priority interrupt handler like a standard application thread, which is fundamentally incorrect.
What ASUS Wrote:
Method (ECLV, 0 , NotSerialized ) { While (events_exist) { process_event(); Sleep (100); // FATAL FLAW: This blocks the entire CPU core. check_timers(); } }
What It Should Be:
Method (ECLV, 0 , NotSerialized ) { // Acknowledge interrupt, queue work, and exit immediately. Local0 = EC0.EEV0; // Read event source EC0.EEV0 = 0 ; // Clear the event source QueueWorkForLater( Local0 ); // Queue a low-priority task Return ; // Exit the handler in microseconds. }
Root Cause 2: Flawed Interrupt Handling
The firmware artificially re-arms the interrupt, creating an endless loop of GPEs instead of clearing the source and waiting for the next legitimate hardware event. This transforms a hardware notification system into a disruptive, periodic timer.
Root Cause 3: Lack of Platform Awareness
The code that sends GPU power notifications does not check if the system is in MUX mode, a critical state check that is correctly performed in other parts of the firmware. This demonstrates inconsistency and a lack of quality control.
Timeline of User Reports
The Three-Year Pattern
This issue is not new or isolated. User reports documenting identical symptoms with high ACPI.sys DPC latency, periodic stuttering, and audio crackling have been accumulating since at least 2021 across ASUS's entire gaming laptop lineup.
August 2021: The First Major Reports
The earliest documented cases appear on the official ASUS ROG forums. A G15 Advantage Edition (G513QY) owner reports "severe DPC latency from ACPI.sys" with audio dropouts occurring under any load condition. The thread, last edited in March 2024, shows the issue remains unresolved after nearly three years.
Reddit users simultaneously report identical ACPI.sys latency problems alongside NVIDIA driver issues; the exact symptoms described in this investigation.
2021-2023: Spreading Across Models
Throughout this period, the issue proliferates across ASUS's gaming lineup:
2023-2024: The Problem Persists in New Models
Even the latest generations aren't immune:
Conclusion
The evidence is undeniable:
Measured Proof: GPE handlers are measured blocking a CPU core for over 13 milliseconds.
GPE handlers are measured blocking a CPU core for over 13 milliseconds. Code Proof: The decompiled firmware explicitly contains Sleep() calls within an interrupt handler.
The decompiled firmware explicitly contains calls within an interrupt handler. Logical Proof: The code lacks critical checks for the laptop's hardware state (MUX mode).
The code lacks critical checks for the laptop's hardware state (MUX mode). Systemic Proof: The issue is reproducible across different models and BIOS versions.
Until a fix is implemented, millions of buyers of Asus laptops from approx. 2021 to present day are facing stutters on the simplest of tasks, such as watching YouTube, for the simple mistake of using a sleep call inside of an inefficient interrupt handler and not checking the GPU environment properly.
The code is there. The traces prove it. ASUS must fix its firmware.
ASUS has not responded to this investigation or the documented firmware issues at the time of publication, will update this if anything changes.
Investigation conducted using the Windows Performance Toolkit, ACPI table extraction tools, and Intel ACPI Component Architecture utilities. All code excerpts are from official ASUS firmware. Traces were captured on multiple affected systems, all showing consistent behavior.