Tech

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Tech 16 Sep 2026 5 min read

USB Selective Suspend Reduces Power for Idle Devices

USB does not require every attached device to remain fully active whenever the computer is running. A host can suspend an idle USB device while other devices continue transferring data. This behavior reduces unnecessary power use, especially on portable systems with several peripherals. The useful distinction is scope: selective suspend targets an idle device or interface rather than treating the entire USB controller as one power unit. Suspend applies to idle USB activity A USB host schedules transfers. When a device has no useful work pending, keeping all of its circuitry active can waste energy.

USB Power Management

Tech 16 Sep 2026 5 min read

PCIe Active State Power Management Trades Idle Power for Exit Latency

A PCI Express link does not need to stay at its fully active electrical state while no traffic is moving. Active State Power Management, commonly shortened to ASPM, lets compatible link partners place the link into lower-power states during idle periods. The practical tradeoff is simple: deeper idle states can save more power, but returning to active operation takes time. That exit delay becomes part of the latency seen when new traffic arrives.

PCIe Power Management