Every USB device generates interrupts. Your mouse, keyboard, headset, and controller all compete for interrupt handling time. On a busy system this affects input latency.
USB interrupt moderation
Windows can moderate USB interrupts — batch them to reduce CPU overhead. For high-polling-rate devices (1000hz+ mice), interrupt moderation adds latency.
Disable USB selective suspend (which causes reconnect delays):
Control Panel → Power Options → Change plan settings → Change advanced power settings → USB Settings → USB selective suspend setting → Disabled
USB controller affinity
USB controllers can be assigned to specific CPU cores via interrupt affinity. By default Windows distributes interrupts across cores automatically. For dedicated gaming, pinning USB interrupts to cores that the game doesn't use can reduce contention.
This is advanced — use msconfig or registry affinity settings. Generally not needed unless LatencyMon shows USB as a DPC latency source.
xHCI vs EHCI
Modern USB 3.x uses xHCI controllers. Older EHCI (USB 2.0) controllers have higher interrupt latency. If you're running a high-polling-rate mouse through a USB 2.0 hub, move it to a direct USB 3.0 port.
Multiple devices on same controller
USB ports share controllers. If your mouse and keyboard share a controller with your audio interface, they compete for interrupt handling. Spread devices across physical USB controllers (check Device Manager to see which ports share controllers).
USB power management
Disable power management on USB hubs:
Device Manager → Universal Serial Bus controllers → each USB Root Hub → Properties → Power Management → uncheck "Allow the computer to turn off this device to save power"
IzanagiOP disables USB selective suspend and USB hub power management globally. https://terweb.lt/
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