Is ‘Sleep’ the same as ‘Suspend’ or ‘Standby’?

Fred langa
By Fred Langa

The sleep-state modes programmed into today’s PCs are rigidly defined, but the common names of these modes vary wildly from vendor to vendor.

With no standardized language, it can be difficult to know exactly what it means when your PC goes into standby mode. But here’s help.


PC still seems active when ‘standing by’

Reader Bob Hall’s PC is supposed to be snoozing, but he still sees activity and wants to know what’s going on in there.
  • “I noticed that even though my computer was in standby mode, the hard drive light was blinking, indicating activity. What’s going on? Am I being a bit paranoid about what might be happening? “
Paranoid? No, you’re just observant.

Most PCs today support several distinct power modes or sleep states, generally defined by the Advanced Configuration and Power Interface (ACPI) specification, an engineering document you’ll find on an ACPI info page. If you’d prefer a plain-English explanation, check out my Langa Letter article, “To Sleep, Perchance to Hibernate.” Virtually all PCs sold today are ACPI-compliant.

ACPI defines six states ranging from S0 (sleep zero) — the PC is fully on — through S5 — it’s completely off. Between those extremes, the various sleep states specify which components in the computer are receiving power and how much.

Although the technical specs of each sleep state are firmly defined, PC vendors often disagree on the labeling they use for sleep modes. Some use nondescriptive names, such as my laptop’s Zzz function keys (evocative of snoring, I guess). Others may refer to reduced-power states as sleep, standby, or suspend, with no further clarification.

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Fred Langa

About Fred Langa

Fred Langa is senior editor. His LangaList Newsletter merged with Windows Secrets on Nov. 16, 2006. Prior to that, Fred was editor of Byte Magazine (1987 to 1991) and editorial director of CMP Media (1991 to 1996), overseeing Windows Magazine and others.