Motherboard manufacturer ASRock just released a feature called "Instant Boot" which presumably reduces Windows XP and Vista boot times down to about 3-4 seconds. After reading through their description of the feature I realized what they had really done was tweak the way the shutdown procedure works so that shutting down your computer places it in a S3 or S4 state. They do this by rebooting your PC and letting Windows reach a stable state after you request a shutdown. The BIOS monitors the OS in memory and sends a call to enter S3 or S4 when Windows stabilizes. Because the S3 state requires power to hold the contents in RAM an S4 "ram-to-disk" image is also taken when S3 is called. The mode that ASRock calls "Fast Mode" uses the S3 state to provide the 3-4 second boot time, "Regular Mode" essentially hibernates the machine so its boot time will be a bit longer.

This is really just a gimmick to increase sales.

When I power down my PC I "Hibernate" it, at the "Turn Off Computer" dialog hold down shift and click yellow button. Hibernate sends the computer into S4 and uses the same amount of power as it would were it shutdown. Hibernate resumes Windows in about 25 seconds and isn't susceptible to power failures.

"Standby" or S3 uses a little power to keep the RAM from loosing its contents, if you pull the plug you should expect a full reboot. It may give you 3-4 second boots but it wastes energy. Use "Standby" if you leave the house for a few hours and can't spare 20 seconds when you return.

"Shutdown/Reboot" is really just a process for clearing out junk memory contents and messing with hardware. Windows occasionally needs a fresh start that only a full RAM wipe can provide, I have to reboot about once a week.

A few weeks ago the topic of boot times crossed my mind and I had an interesting idea that seems similar to ASRock's feature. If S3 leaves the RAM data intact why can't the BIOS handle the storage of that data onto a dedicated solid state disk on the motherboard. 8Gb memory sticks are already dirt cheap, the same silicon could be used for this purpose. If the computer never looses power it resumes from S3 as usual. If the RAM is cleared for some reason then the BIOS reloads the RAM from its solid state image and Windows still resumes from S3. This could drop S4 resume times as well. Hopefully we'll see something like this show up in response to ASRock's market ploy.