As I found out, a lot! This is one of those things that you might not think about, but that makes a lot of sense once you figure it out…
After installing Windows 2003 Server on a laptop, and loading Toshiba Power Saver utility, I thought I would finally get the “Stand by” option for the “When I close the lid of my portable computer” setting… But no, all I had was the “Do nothing” option.
Given that I was running an operating system intended for servers, not personal computers, I started doubting whether it was a supported option. But thanks to Allen Marshall, my problem was simple – install the “real” device driver for my graphics adapter, instead of the standard VGA driver! Allen suggested to run powercfg /a command at the command prompt – vga.sys was the dead give-away that I forgot to install the driver that supports the stand-by sleep state.
When you run the powercfg command, you’ll get information on S1, S2, S3 support by your device driver… In summary, in the S1 state, only the processor and its clocks are halted – this still draws significant power; not very interesting on a mobile, and almost never used on desktops anymore. S2 is defined by the ACPI spec, but rarely, if ever, implemented. S3 is the Suspend to RAM state, where memory is put in self-refresh and the vast majority of your platform is switched off. Very low power on a laptop (~0.5W); you can stay in this state for days, and typically only lose 1% of battery per hour of S3 time.