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I just replaced a busted motherboard on my Windows 7 computer, and it no longer sleeps as it had before. With my old motherboard, whenever I put the computer to sleep, the screen faded to black and then the computer turned off after a bit. Then, when I turned it back on, it went straight to the login screen. This felt more akin to hibernation, except that the computer was able to resume right away.

With my new motherboard, going to sleep does not turn off the computer. The screen goes black as before, and the computer resumes right away when I press the power button, but the power supply keeps running at full force. The hard drive and other components turn off, but the computer does not.

What explains this difference in behavior? Is this a motherboard/BIOS feature, or is something broken?

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up vote 5 down vote accepted

Looks like your old mainboard was using the "S3 mode" (Suspend to RAM, only RAM requires power) and your new mainboard only uses the "S1 mode" (Standby, nearly every component is still powered).

Most mainboards allow in the BIOS to specify whether the S1 or S3 mode should be used.

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The S3 option was there under ACPI settings and made everything work like before. Thank you! – Archagon Oct 28 '11 at 4:47

Are you sure that the power supply keeps delivering energy? I assume that it is just the fan that spins, which would mean that you old board had a feature to switch the power supplies fan off and you newer one does not.

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I think the video card spins as well. I'd like to know what this feature is called, if it exists, so that I can look out for it when buying my next motherboard. – Archagon Oct 27 '11 at 8:18
Can you check which devices keep working exactly? – Michael K Oct 27 '11 at 8:46

Put your monitor to sleep. A computer that sleeps then wakes up, is like a human, it's sluggish, In my view, its better to let the pc run, idle and have the screen(s) asleep

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This answer doesn't explain the cause of the difference in behaviour. – miyalys Oct 4 '15 at 19:13

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