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What processes, if any, run while my computer is put to sleep (not hibernation mode)?

For example, if there's an application which prints a line every second to a file, will it print lines while the computer is asleep? If I have an application running doing video conversion, would it continue its process while the computer is sleeping? If I have an IM application running, will I receive messages while the computer sleeps?

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To my knowledge, only volatile memory is powered during sleep. So pretty much all applications are kept in memory, but all other hardware is powered down. All in all @mankoff hit it on the head with his answer. – Ryan Wersal Feb 14 '11 at 2:19
up vote 16 down vote accepted

Nothing will run while the computer is asleep. Unlike humans, where sleep is different than death, when a computer sleeps it is essentially equal to being powered off.

There are a few subtle differences, the primary being that it wakes up faster than from a cold boot. This is because there is enough power supplied to the RAM (memory) to keep it active, but this does not mean there is power supplied to the CPU (heart), or that any processes are active.

Any processes that are active are below the operating system, in the BIOS of the computer. This is where the "Wake On Lan" feature resides, for example.

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+1 For teaching us that asleep is different than dead. – Petruza Feb 14 '11 at 4:11
I'm pretty sure things like Wake on Lan are handled by the SMC (system management controller), which isn't so much below the OS (which lives on the CPU) as beside it. – Gordon Davisson Feb 14 '11 at 4:14

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