While testing a PC with Vista 64, I noticed that it would “sleep”, but then not come back to “life”.

I’d end up having to press the power button twice, and then Vista would complain that it wasn’t restored correctly from sleep.

I had adjusted some bios settings (a DP45SG motherboard), so I looked at those first, and narrowed it down to either: “EIST”, “S3 sleep state”, “VT”, or “UEFI”.

A bit of research later, and I now understand what those abbreviations mean.

It turned out that the problem was due to UEFI being enabled.

UEFI (Unified Extended Firmware Interface) is supposed to be a good thing, as it allows for (amongst other things) booting from hard drives bigger that 2Tb… not needed right now, but drives bigger than 2Tb are just around the corner.

But it seems that proper motherboard support for UFEI is still not quite right.

So, I disable UEFI, and Vista started “sleeping like a baby” 🙂

And if you want to know about EIST: its really just speedstep… the motherboard dynamically lowers the FSB multiplier… so that CPU, RAM, etc runs slower, use less power, and generate less heat… but it switches to full speed when needed.