DEV Community: Izanagi

IRQ priority and MSI mode: the GPU interrupt optimization

Izanagi — Thu, 23 Jul 2026 10:00:34 +0000

Every time your GPU finishes rendering a frame, it signals the CPU via an interrupt. How that interrupt is handled affects frame delivery latency.

Legacy INTx vs MSI

By default, GPUs use legacy INTx interrupts — a shared hardware signal. Multiple devices share the same interrupt line, and the driver has to check which device fired it.

MSI (Message Signaled Interrupts) sends interrupts as memory writes directly to the CPU. They're per-device, so no sharing, no check required. Lower latency, more reliable.

Most modern GPUs support MSI but Windows doesn't always enable it automatically.

Enabling MSI mode for GPU

Find your GPU's device instance path in Device Manager (right-click → Properties → Details → Device Instance Path).

Then in registry:

HKLM\SYSTEM\CurrentControlSet\Enum\<device-path>\Device Parameters\Interrupt Management\MessageSignaledInterruptProperties
MSISupported = 1

Also set IRQ priority:

HKLM\SYSTEM\CurrentControlSet\Enum\<device-path>\Device Parameters\Interrupt Management\Affinity Policy
DevicePriority = 3

Audio device too

The same MSI mode treatment applies to your audio device. GPU and audio on MSI mode together reduce DPC latency — measurable with LatencyMon.

IzanagiOP's Aggressive Optimizations pack handles GPU and audio MSI mode automatically using the correct device paths for your hardware. https://terweb.lt/

What GPU priority settings in registry actually do

Izanagi — Wed, 22 Jul 2026 10:00:33 +0000

There are two GPU priority settings in Windows that most optimization guides mention but few explain correctly.

GpuPriority in IFEO

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\game.exe\PerfOptions
GpuPriority = 8

This sets the GPU engine priority for threads spawned by the process. Range is 0-8, where 8 is highest. Higher priority means the GPU scheduler prefers this process when deciding what to execute next on the GPU command queue.

On busy systems with overlays, browsers, and other GPU consumers running alongside games, this gives the game priority access to GPU execution time.

GPU Priority in MMCSS

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks\Games
GPU Priority = 8

This is the MMCSS-level GPU priority applied to threads registered under the "Games" MMCSS task. It affects the Windows GPU scheduler independently from the IFEO setting.

Both should be set to 8 for gaming.

What you see

These settings don't typically change average FPS significantly. What changes is consistency — the GPU is less likely to be interrupted by DWM compositing or overlay rendering mid-frame. This shows in frame time graphs as fewer outlier spikes.

IzanagiOP sets both via the Trajectory Pack (per-game IFEO) and HitSync Pack (MMCSS). https://terweb.lt/

How Windows power plans actually affect gaming performance

Izanagi — Tue, 21 Jul 2026 10:00:32 +0000

Most people know to switch from Balanced to High Performance. Fewer know what the difference actually is — or that there's a third option that outperforms both for gaming.

Balanced power plan

Dynamically scales CPU frequency based on load. When load drops, frequency drops. When load rises, there's a ramp-up period before the CPU hits full speed.

For gaming with variable load (menu → combat → menu), this creates micro-stutters as the CPU spins up to handle sudden load spikes.

High Performance

Keeps CPU frequency higher on average but still allows some scaling. Core parking may still be active depending on your system.

Ultimate Performance

Introduced in Windows 10 1803. Removes all frequency scaling — CPU stays at maximum at all times. Also disables:

Core parking
Hard disk timeout
USB selective suspend
PCIe link state power management

# Activate Ultimate Performance
powercfg /duplicatescheme e9a42b02-d5df-448d-aa00-03f14749eb61
# Copy the GUID from output, then:
powercfg /setactive <GUID>

The catch

Maximum power draw and heat. For desktops: no issue. For laptops: battery drains faster, thermals run hotter.

Locking it in

IzanagiOP activates Ultimate Performance and locks it so Windows Update or driver installs don't reset it back to Balanced. https://terweb.lt/

Roblox FPS unlocker isn't enough — fix Windows too

Izanagi — Mon, 20 Jul 2026 10:00:31 +0000

The Roblox FPS unlocker removes the 60fps cap. But if your hardware should push 144+ and you're stuck at 80-90, the bottleneck is Windows scheduling, not the unlocker.

Why Roblox tanks

Roblox's engine is single-threaded for game logic. One CPU core does most of the work. Windows needs to schedule that core at maximum priority and keep it there.

Core priority

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\RobloxPlayerBeta.exe\PerfOptions
CpuPriorityClass = 3
IoPriority = 3
GpuPriority = 8

Disable Power Throttling

Windows 10/11 throttles "background" processes using EcoQoS. Sometimes Roblox gets misclassified:

HKLM\SYSTEM\CurrentControlSet\Control\Power\PowerThrottling
PowerThrottlingOff = 1

CPU parking off

Parked cores have a spin-up delay. For Roblox where load is sudden (new area, many players):

powercfg /setacvalueindex scheme_current sub_processor 0cc5b647-c1df-4637-891a-dec35c318583 100
powercfg /setactive scheme_current

Clean Roblox logs

Roblox accumulates logs in %localappdata%\Roblox\logs. These can grow to several GB and cause I/O overhead on startup. Delete them periodically.

IzanagiOP handles per-game priorities, log cleanup, and power settings automatically. https://terweb.lt/

League of Legends low FPS fix: what Windows is doing wrong

Izanagi — Sun, 19 Jul 2026 10:00:29 +0000

League of Legends is not a demanding game. If you're getting low FPS on hardware that should handle it easily, Windows configuration is almost always the reason.

Background process interference

LoL runs the Riot Client, LeagueClient.exe, and League of Legends.exe simultaneously. The client processes consume CPU and RAM while the game runs. Combined with Windows background services, the game thread gets squeezed.

Disable unnecessary services during gaming

These services run constantly and provide no benefit while gaming:

SysMain (Superfetch): preloads apps into RAM. Irrelevant on SSD.
Windows Search (WSearch): indexes files in the background. Causes disk I/O spikes.
DiagTrack: sends telemetry. Pure overhead.
Connected User Experiences: more telemetry.

sc config SysMain start= disabled
sc config WSearch start= disabled
sc config DiagTrack start= disabled
sc config dmwappushservice start= disabled

Per-process priority

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\League of Legends.exe\PerfOptions
CpuPriorityClass = 3
IoPriority = 3
GpuPriority = 8

Visual FX

Control Panel → System → Advanced → Performance Settings → Adjust for best performance. Removes all animations and transparency that DWM has to render alongside your game.

Power plan

If you're on balanced power plan, your CPU is throttling frequencies dynamically. Switch to Ultimate Performance.

Full automated setup: https://terweb.lt/

Overwatch 2 stutter fix: the DWM and MPO connection

Izanagi — Sat, 18 Jul 2026 10:00:28 +0000

Overwatch 2 stutter is one of the most common complaints in the community. Most people blame the game. The actual cause is usually Windows Desktop Window Manager and Multi-Plane Overlay.

What MPO does in practice

MPO (Multi-Plane Overlay) lets the GPU compositor handle overlay layers independently. In theory it reduces composite latency. In practice it causes frame delivery to become irregular on a wide range of hardware — especially AMD GPUs but also certain NVIDIA configurations.

Blizzard has acknowledged frame pacing issues in OW2. The fix on their end is ongoing. The fix on your end takes 30 seconds.

Disable MPO

HKCU\Software\Microsoft\Windows\DWM
OverlayTestMode = 5

Log out and back in, or reboot.

Disable Fullscreen Optimizations

HKCU\System\GameConfigStore
GameDVR_FSEBehaviorMode = 2
GameDVR_FSEBehavior = 2

DXGI latency

HKLM\SOFTWARE\Microsoft\DirectX
MaxFrameLatency = 1

Game DVR off

HKCU\System\GameConfigStore
GameDVR_Enabled = 0

These four changes together address the most common source of OW2 stutter that isn't related to the game itself.

IzanagiOP's Frame Pack applies all of them plus DWM timer, transparency, and fullscreen optimization settings. https://terweb.lt/

Apex Legends FPS optimization: CPU scheduling and why it matters

Izanagi — Fri, 17 Jul 2026 10:00:27 +0000

Apex Legends runs on a modified Source engine that's heavily CPU-dependent. If your average FPS looks fine but 1% lows are rough — that's scheduling, not hardware.

The core issue

Apex spawns multiple threads: render thread, game logic, audio, network. Windows default scheduling doesn't distinguish between these and your browser tabs. All compete equally.

Per-process priority

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\r5apex.exe\PerfOptions
CpuPriorityClass = 3
IoPriority = 3
GpuPriority = 8

This applies every time Apex launches — no need to set it manually each session.

Power plan

Ultimate Performance plan disables core parking and locks CPU frequency:

powercfg /duplicatescheme e9a42b02-d5df-448d-aa00-03f14749eb61
powercfg /setactive <guid>

Standard High Performance still allows frequency scaling. Ultimate Performance doesn't.

Win32PrioritySeparation

HKLM\SYSTEM\CurrentControlSet\Control\PriorityControl
Win32PrioritySeparation = 38

Short scheduling quanta, 3x foreground priority. Game thread gets scheduled more often per second.

Result

With these changes the 1% lows align much closer to average FPS. The game feels smoother even if the counter reads the same.

Full automated setup at https://terweb.lt/ — IzanagiOP handles all of this plus 500+ more tweaks across system, network, and audio.

Mouse input latency on Windows: the full picture

Izanagi — Thu, 16 Jul 2026 10:00:26 +0000

Mouse input latency is one of the most discussed topics in competitive gaming and one of the least well-understood. Here's every layer that adds latency between your physical mouse movement and what the game sees.

The path from hardware to game

Mouse sensor detects movement
Mouse firmware processes it and sends USB report
Windows USB driver receives the report (interrupt)
mouclass.sys adds the event to a queue
win32k.sys reads from the queue
Game reads raw input via DirectInput or Win32 Raw Input API

Each step has a potential delay.

USB polling rate

Your mouse sends reports at a fixed rate — 125hz (8ms), 250hz (4ms), 500hz (2ms), or 1000hz (1ms). At 1000hz, the maximum additional latency from polling is 1ms.

Most gaming mice default to 1000hz. Check your mouse software.

mouclass queue depth

Windows maintains a queue for mouse input events. The default queue depth is 100 events. Before that, MouseDataQueueSize used to matter more — at high polling rates with a backed-up queue, events could be delayed.

Modern systems process the queue fast enough that this is rarely the bottleneck, but setting it lower (16 or 32) doesn't hurt.

HKLM\SYSTEM\CurrentControlSet\Services\mouclass\Parameters
MouseDataQueueSize = 16

Mouse acceleration (Pointer Precision)

Windows applies an acceleration curve to mouse input by default ("Enhance Pointer Precision"). This is not linear — faster movements are amplified more than slow movements. For gaming, this makes muscle memory inconsistent.

Turn it off in Mouse settings → Pointer Options → uncheck "Enhance pointer precision."

Or via registry:

HKCU\Control Panel\Mouse
MouseSpeed = 0
MouseThreshold1 = 0
MouseThreshold2 = 0

Also remove the acceleration curves entirely:

reg delete "HKCU\Control Panel\Mouse" /v SmoothMouseXCurve /f
reg delete "HKCU\Control Panel\Mouse" /v SmoothMouseYCurve /f

Cursor shadow

A small one, but cursor shadow adds a DWM render pass per frame. Disabling it reduces DWM overhead slightly:

HKCU\Control Panel\Desktop
CursorShadow = 0

Snap to default button

Windows can "snap" your cursor to the default button in dialogs. This can cause unwanted cursor movement. Disable:

HKCU\Control Panel\Mouse
SnapToDefaultButton = 0

All of the above is in IzanagiOP's Trajectory Pack alongside per-game CPU/IO/GPU priorities and network NIC settings. Discord: https://terweb.lt/

Disable Spectre and Meltdown mitigations on Windows — performance vs security tradeoff

Izanagi — Wed, 15 Jul 2026 10:00:25 +0000

Spectre and Meltdown are CPU vulnerabilities discovered in 2018. Microsoft patched them via Windows updates, but the patches have a CPU performance cost. Whether to disable them is a genuine tradeoff worth understanding.

What the mitigations do

The patches work by preventing speculative execution from accessing memory it shouldn't. This is done by flushing the CPU pipeline more aggressively at certain points — kernel/user mode transitions, process context switches, indirect branch instructions.

The performance cost varies by workload:

Games (mostly GPU-bound): 1-5% CPU overhead
Database workloads, system calls-heavy code: 10-30% overhead
Memory-intensive tasks: variable

The registry toggle

HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management
FeatureSettingsOverride = 3
FeatureSettingsOverrideMask = 3

Setting both to 3 disables the Spectre and Meltdown mitigations. A reboot is required.

To re-enable:

FeatureSettingsOverride = 0
FeatureSettingsOverrideMask = 3

Should you do it?

On a gaming PC that doesn't run web servers or handle untrusted code: the real attack surface for Spectre/Meltdown is fairly limited. The vulnerabilities require local code execution — if malware is already running on your system, you have bigger problems than Spectre.

On a machine that runs shared services, VMs, or handles sensitive data: keep the mitigations on.

For the average gaming desktop: the risk is low and the performance gain is real. Make an informed decision.

This tweak is in IzanagiOP's Spread Pack. It's not applied by default — it's opt-in because it's a conscious tradeoff. Discord: https://terweb.lt/

IzanagiOP: a Windows optimizer built on actual registry research

Izanagi — Tue, 14 Jul 2026 10:00:25 +0000

I've been building Windows optimization tools for a few years. Most optimizers I've seen fall into two categories: batch scripts that blindly apply settings from a 2018 Reddit post, or GUI wrappers around the same scripts with a checkbox per setting.

IzanagiOP started as a personal project — a C++ application that systematically addresses every layer of Windows that affects game performance. After using it with a group of FiveM and CS2 players and seeing consistent results, I turned it into a product.

What makes it different

Vendor detection. The app detects your GPU vendor (NVIDIA/AMD/Intel) via CPUID and EnumDisplayDevices. Tweaks that only apply to specific hardware — NVIDIA Low Latency Mode, AMD shader cache cleanup, HAGS behavior — are gated accordingly. HAGS is excluded from Frame Pack because it causes screen flicker on AMD Navi GPUs. Most tools enable it blindly.

Direct WinAPI. The app routes registry changes through the Windows API directly rather than spawning reg.exe child processes. This avoids false-positive antivirus alerts triggered by reg add commands in child processes.

Full revert. Every applied tweak can be undone. The app shows you what's changed and what the original value was.

Precision Packs. Beyond general optimizations, there are packs designed for specific in-game behaviors: Trajectory Pack (sniper/mouse accuracy), Spread Pack (sustained fire CPU consistency), Scatter Pack (network stack for shotgun/spray patterns), HitSync Pack (server-side timing alignment), Audio Pack (latency reduction), Frame Pack (frame pacing and DWM).

Cleaner. 100+ individual cache and temp targets — system caches, browser caches, game launcher caches (Steam, Discord, Epic, Battle.net, EA, Roblox, Valorant logs), development tool caches (npm). All individually selectable.

Numbers from users

FiveM: 60/70fps → 120/160fps
FiveM: 70/90fps → 140fps
Fortnite: 120fps → 300fps, 30ms ping → 13ms ping
CS2: +70-80fps
General: 120fps → 200fps in various games

Technical stack

C++, ImGui, DirectX 11. Single .exe, no installer, no background services. License system via Discord.

Pricing: €5/month or €10 lifetime. Discord: https://terweb.lt/

MMCSS explained: why your game thread gets starved and how to fix it

Izanagi — Mon, 13 Jul 2026 10:00:24 +0000

MMCSS — Multimedia Class Scheduler Service — is Windows' mechanism for giving time-critical threads priority access to CPU resources. Games and audio applications use it. Most people have never touched the configuration.

How it works

Applications call AvSetMmThreadCharacteristics() to register with MMCSS under a named task (like "Games" or "Audio"). MMCSS then boosts that thread's priority and gives it a higher percentage of CPU time.

The configuration for each task lives in the registry:

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks\Games

Default values vs gaming-optimal values

Setting	Default	Gaming
Priority	2	6
Scheduling Category	Medium	High
GPU Priority	8	8
SFIO Priority	Normal	High
Background Only	True	False

The default Priority of 2 means your game thread competes with most other threads. Setting it to 6 with High scheduling category moves it to a tier where only system-critical threads can preempt it.

SystemResponsiveness

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile
SystemResponsiveness = 0

This controls how much CPU time MMCSS reserves for non-multimedia tasks. Default is 20% (Windows reserves 20% of CPU for background processes even when a multimedia task needs it). Setting it to 0 allows MMCSS tasks to use 100% of CPU when needed.

NetworkThrottlingIndex

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile
NetworkThrottlingIndex = 4294967295

By default, Windows throttles network processing when MMCSS tasks are running (to protect the game from network interrupts). Setting this to max disables the throttling — useful when you want both game priority AND network performance.

IzanagiOP configures the full MMCSS suite: Games, Audio, Playback, DisplayPostProcessing, Capture. All priority values are set to gaming-optimal. Discord: https://terweb.lt/

The difference between Safe, Medium, and Aggressive Windows optimization

Izanagi — Sun, 12 Jul 2026 10:00:23 +0000

When people talk about Windows optimization, there's a spectrum from "low risk, low impact" to "high impact, might break something." Understanding which tweaks fall where helps you make informed decisions.

Safe optimizations

These are changes that have well-understood behavior and virtually no downside for gaming setups:

Disable Game DVR / Xbox Game Bar: removes background GPU encoder. Zero downside if you don't stream.
Disable Mouse Pointer Precision: removes the acceleration curve from mouse input. Essential for FPS games.
Visual FX to Best Performance: removes window animations and transparency. No functional loss.
Disable Fast Startup: fast startup is actually a partial hibernate, which can cause driver and scheduler state issues. Real cold boot is more reliable.
NIC power settings: disabling Energy Efficient Ethernet and Wake on Magic Packet has no practical downside on a gaming PC.
Disable telemetry tasks: scheduled tasks that report usage data to Microsoft. Removing them frees up CPU/disk time without affecting any feature you use.

Medium optimizations

Higher impact, still appropriate for most gaming setups but worth understanding:

Ultimate Performance power plan: locks all cores at max frequency. Increases power draw and heat. Fine for desktops; think twice on laptops.
Disable Hibernate: frees up several GB (hiberfil.sys). You lose the ability to hibernate — fast shutdown with state preservation. Fine if you never use it.
Timer resolution to 0.5ms: requires bcdedit changes. Stable on modern hardware, rare edge cases on very old systems.
HAGS (AMD excluded): improves GPU scheduling on NVIDIA, causes flicker on AMD Navi.
Disable telemetry services: stops data collection services. Some enterprise features depend on these.

Aggressive optimizations

These have real tradeoffs:

Disable SysMain: removes prefetching. On HDDs this slows cold app launches. On SSDs it's fine.
Disable Memory Compression: reduces CPU usage from compression but means RAM fills faster. Need enough RAM (16GB+).
Pagefile changes: setting a fixed pagefile size prevents Windows from dynamically adjusting it. Wrong size causes issues.
Disable CPU C-States: keeps CPU fully awake at all times. Maximum performance, maximum power draw.
Spectre/Meltdown mitigations disable: real CPU performance gain, real security reduction. Your call.

IzanagiOP splits tweaks into these three categories + precision packs. You apply what makes sense for your setup. Discord: https://terweb.lt/